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1 Object-oriented programming (OOP) is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction, encapsulation, messaging, modularity, polymorphism, and inheritance. Many modern programming languages now support OOP, at least as an option. In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure. (With the later introduction of object-oriented programming the same word, "object", refers to a particular instance of a class)

2 In the domain of object-oriented programming an object is usually taken to mean an ephemeral compilation of attributes (object elements) and behaviors (methods or subroutines) encapsulating an entity. In this way, while primitive or simple data types are still just single pieces of information, object-oriented objects are complex types that have multiple pieces of information and specific properties (or attributes). Instead of merely being assigned a value, (like int =10), objects have to be "constructed". In the real world, if a Ford Focus is an "object" - an instance of the car class, its physical properties and its function to drive would have been individually specified. Once the properties of the Ford Focus "object" had been specified into the form of the car class, it can be endlessly copied to create identical objects that look and function in just the same way. As an alternative example, animal is a superclass of primate and primate is a superclass of human. Individuals such as Joe Bloggs or John Doe would be particular examples or 'objects' of the human class, and consequently possess all the characteristics of the human class (and of the primate and animal superclasses as well).

3 "Objects" are the foundation of object-oriented programming, and are fundamental data types in object-oriented programming languages. These languages provide extensive syntactic and semantic support for object handling, including a hierarchical type system, special notation for declaring and calling methods, and facilities for hiding selected fields from client programmers. However, objects and object-oriented programming can be implemented in any language.

4 Objects are used in software development to implement abstract data structures, by bringing together the data components with the procedures that manipulate them. Objects in object- oriented programming are key in the concept of inheritance; thereby improving program reliability[attribution needed], simplification of software maintenance[attribution needed], the management of libraries, and the division of work in programmer teams. Object-oriented programming languages are generally designed to exploit and enforce these potential advantages of the object model. Objects can also make it possible to handle very disparate objects by the same piece of code, as long as they all have the proper method. Simple, non-OOP programs may be one "long" list of statements (or commands). More complex programs will often group smaller sections of these statements into functions or subroutines each of which might perform a particular task. With designs of this sort, it is common for some of the program's data to be 'global', i.e. accessible from any part of the program. As programs grow in size, allowing any function to modify any piece of data means that bugs can have wide-reaching effects.

5 In contrast, the object-oriented approach encourages the programmer to place data where it is not directly accessible by the rest of the program. Instead, the data is accessed by calling specially written functions, commonly called methods, which are either bundled in with the data or inherited from "class objects." These act as the intermediaries for retrieving or modifying the data they control. The programming construct that combines data with a set of methods for accessing and managing those data is called an object. The practice of using subroutines to examine or modify certain kinds of data, however, was also quite commonly used in non-OOP modular programming, well before the widespread use of object-oriented programming.

6 An object-oriented program will usually contain different types of objects, each type corresponding to a particular kind of complex data to be managed or perhaps to a real-world object or concept such as a bank account, a hockey player, or a bulldozer. A program might well contain multiple copies of each type of object, one for each of the real-world objects the program is dealing with. For instance, there could be one bank account object for each real-world account at a particular bank. Each copy of the bank account object would be alike in the methods it offers for manipulating or reading its data, but the data inside each object would differ reflecting the different history of each account.

7 Objects can be thought of as wrapping their data within a set of functions designed to ensure that the data are used appropriately, and to assist in that use. The object's methods will typically include checks and safeguards that are specific to the types of data the object contains. An object can also offer simple-to-use, standardized methods for performing particular operations on its data, while concealing the specifics of how those tasks are accomplished. In this way alterations can be made to the internal structure or methods of an object without requiring that the rest of the program be modified. This approach can also be used to offer standardized methods across different types of objects. As an example, several different types of objects might offer print methods. Each type of object might implement that print method in a different way, reflecting the different kinds of data each contains, but all the different print methods might be called in the same standardized manner from elsewhere in the program. These features become especially useful when more than one programmer is contributing code to a project or when the goal is to reuse code between projects.

9 An object-oriented program may thus be viewed as a collection of interacting objects, as opposed to the conventional model, in which a program is seen as a list of tasks (subroutines) to perform. In OOP, each object is capable of receiving messages, processing data, and sending messages to other objects. Each object can be viewed as an independent "machine" with a distinct role or responsibility. The actions (or "methods") on these objects. The terms "objects" and "oriented" in something like the modern sense of object- oriented programming seem to make their first appearance at MIT in the late 1950s and early 1960s. In the environment of the artificial intelligence group, as early as 1960, "object" could refer to identified items (LISP atoms) with properties (attributes); Alan Kay was later to cite a detailed understanding of LISP internals as a strong influence on his thinking in 1966.[3] Another early MIT example was Sketchpad created by Ivan Sutherland in 1960-61; in the glossary of the 1963 technical report based on his dissertation about Sketchpad, Sutherland defined notions of "object" and "instance" (with the class concept covered by "master" or "definition"), albeit specialized to graphical interaction. Also, an MIT ALGOL version, AED-0, linked data structures ("plexes", in that dialect) directly with procedures, prefiguring what were later termed "messages", "methods" and "member functions".

10 Objects as a formal concept in programming were introduced in the 1960s in Simula 67, a major revision of Simula I, a programming language designed for discrete event simulation, created by Ole-Johan Dahl and Kristen Nygaard of the Norwegian Computing Center in Oslo. Simula 67 was influenced by SIMSCRIPT and Hoare's proposed "record classes". Simula introduced the notion of classes and instances or objects (as well as subclasses, virtual methods, coroutines, and discrete event simulation) as part of an explicit programming paradigm. The language also used automatic garbage collection that had been invented earlier for the functional programming language Lisp. Simula was used for physical modeling, such as models to study and improve the movement of ships and their content through cargo ports. The ideas of Simula 67 influenced many later languages, including Smalltalk, derivatives of LISP (CLOS), Object Pascal, and C++.

12 In the 1970s, Kay's Smalltalk work had influenced the Lisp community to incorporate object- based techniques that were introduced to developers via the Lisp machine. Experimentation with various extensions to Lisp (like LOOPS and Flavors introducing multiple inheritance and mixins), eventually led to the Common Lisp Object System (CLOS, a part of the first standardized object-oriented programming language, ANSI Common Lisp), which integrates functional programming and object-oriented programming and allows extension via a Meta- object protocol. In the 1980s, there were a few attempts to design processor architectures that included hardware support for objects in memory but these were not successful. Examples include the Intel iAPX 432 and the Linn Smart Rekursiv.

14 At ETH Z?rich, Niklaus Wirth and his colleagues had also been investigating such topics as data abstraction and modular programming (although this had been in common use in the 1960s or earlier). Modula-2 (1978) included both, and their succeeding design, Oberon, included a distinctive approach to object orientation, classes, and such. The approach is unlike Smalltalk, and very unlike C++.

19 Not all of these concepts are to be found in all object-oriented programming languages. For example, object-oriented programming that uses classes is sometimes called class-based programming, while prototype-based programming does not typically use classes. As a result, a significantly different yet analogous terminology is used to define the concepts of object and instance.

21 Dynamic dispatch – when a method is invoked on an object, the object itself determines what code gets executed by looking up the method at run time in a table associated with the object. This feature distinguishes an object from an abstract data type (or module), which has a fixed (static) implementation of the operations for all instances. It is a programming methodology that gives modular component development while at the same time being very efficient.

24 Object inheritance (or delegation)

25 Open recursion – a special variable (syntactically it may be a keyword), usually called this or self, that allows a method body to invoke another method body of the same object. This variable is late-bound; it allows a method defined in one class to invoke another method that is defined later, in some subclass thereof.

33 Decoupling refers to careful controls that separate code modules from particular use cases, which increases code re-usability. A common use of decoupling in OOP is to polymorphically decouple the encapsulation (see Bridge pattern and Adapter pattern) - for example, using a method interface which an encapsulated object must satisfy, as opposed to using the object's class.

41 Attempts to find a consensus definition or theory behind objects have not proven very successful (however, see Abadi & Cardelli, A Theory of Objects[18] for formal definitions of many OOP concepts and constructs), and often diverge widely. For example, some definitions focus on mental activities, and some on program structuring. One of the simpler definitions is that OOP is the act of using "map" data structures or arrays that can contain functions and pointers to other maps, all with some syntactic and scoping sugar on top. Inheritance can be performed by cloning the maps (sometimes called "prototyping"). OBJECT:=>> Objects are the run time entities in an object-oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program has to handle.

45 Simula (1967) is generally accepted as the first language to have the primary features of an object-oriented language. It was created for making simulation programs, in which what came to be called objects were the most important information representation. Smalltalk (1972 to 1980) is arguably the canonical example, and the one with which much of the theory of object-oriented programming was developed. Concerning the degree of object orientation, following distinction can be made:

46 Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Scala, Smalltalk, Eiffel, JADE, Emerald.

52 In recent years, object-oriented programming has become especially popular in dynamic programming languages. Python, Ruby and Groovy are dynamic languages built on OOP principles, while Perl and PHP have been adding object oriented features since Perl 5 and PHP 4, and ColdFusion since version 5.

53 The Document Object Model of HTML, XHTML, and XML documents on the Internet have bindings to the popular JavaScript

54 ECMAScript language. JavaScript is perhaps the best known prototype- based programming language, which employs cloning from prototypes rather than inheriting from a class. Another scripting language that takes this approach is Lua. Earlier versions of ActionScript (a partial superset of the ECMA-262 R3, otherwise known as ECMAScript) also used a prototype-based object model. Later versions of ActionScript incorporate a combination of classification and prototype-based object models based largely on the currently incomplete ECMA-262 R4 specification, which has its roots in an early JavaScript 2 Proposal. Microsoft's JScript.NET also includes a mash-up of object models based on the same proposal, and is also a superset of the ECMA-262 R3 specification.

56 It is intuitive to assume that inheritance creates a semantic "is a" relationship, and thus to infer that objects instantiated from subclasses can always be safely used instead of those instantiated from the superclass. This intuition is unfortunately false in most OOP languages, in particular in all those that allow mutable objects. Subtype polymorphism as enforced by the type checker in OOP languages (with mutable objects) cannot guarantee behavioral subtyping in any context. Behavioral subtyping is undecidable in general, so it cannot be implemented by a program (compiler). Class or object hierarchies need to be carefully designed considering possible incorrect uses that cannot be detected syntactically. This issue is known as the Liskov substitution principle.

62 Main articles: Object-Relational impedance mismatch, Object-relational mapping, and Object database

64 There are also object databases that can be used to replace RDBMSs, but these have not been as technically and commercially successful as RDBMSs.

80 Steve Yegge, making a roundabout comparison with Functional programming, writes, "Object Oriented Programming puts the Nouns first and foremost. Why would you go to such lengths to put one part of speech on a pedestal? Why should one kind of concept take precedence over another? It's not as if OOP has suddenly made verbs less important in the way we actually think. It's a strangely skewed perspective."

81 Rich Hickey, creator of Clojure, described object systems as over simplistic models of the real world. He emphasized the inability of OOP to model time properly, which is getting increasingly problematic as software systems become more concurrent.

83 There are many definitions of an object, such as found in [Booch 91, p77]:

84 "An object has state, behavior, and identity; the structure and behavior of

86 object are interchangeable". This is a "classical languages" definition, as

88 object model", since they do not in prototyping

90 "The term object was first formally applied in the Simula language, and

93 Smith and Tockey: "an object represents an individual, identifiable item,

98 in depth. [Martin 92, p 241] defines: "An "object" is anything to which a

101 object as a concept, abstraction or thing with crisp boundaries and meaning for

102 the problem at hand." [Shlaer 88, p 14] defines: "An object is an abstraction

114 object categories [Jacobson 94]:

116 Use-Cases and Actors - Actors <--> Use-Cases <--> Object Model Objects

120 Application Objects - In the Object Model

137 oriented databases and operating systems (object id's). A "proxy" based

159 function taking an object of the record type, called the receiver, as the

189 flexible kind of object which can play the role of classes in classical OO

200 fields, methods and parents and any object can be used as a template

206 classification where any object can be inherited from or cloned to serve as a

211 It is common in such systems for an object to "become" another kind of object

227 1.2) What Is Object Encapsulation (Or Protection)? (Object-Oriented Technology)

229 details of an object that do not contribute to its essential characteristics."

237 Object Pascal provide no protection for objects, meaning instance variables

263 object of that class and not just the receiver. Methods can only access the

265 object other than the receiver is only satisfying an abstract type interface,

266 whereby no method or object structure can be inferred in the general case.

286 behavior." "A single object is simply an instance of a class."

297 A Meta-Class is a class' class. If a class is an object, then that object

312 There is only 1 kind of object.

331 object

342 In the authors opinion, a myth. The story goes an object is an instance of a

369 and constructing object systems. Natural means we use concepts,

387 (Ada95, Modula-3, Object Pascal, etc.) OO languages do, but with multiple-

400 specify required attributes of a matching object (see sections 2.1, 2.7 and

405 used synonymously, but can be used to show the "object is-a class"

407 between classes only. In one-level systems, is-a (object instantiation) and

498 (typing based on subclassing, or subclass polymorphism), since only an object

536 a method is invoked on an object of the base class, the derived class method

553 object-oriented = data abstractions + object types + type inheritance

559 Stroustrup's first edition of [Stroustrup 91, '86 p. 37] defines object based

560 as: "... storing type identification in each object, brings us to a style of

561 programming often referred to as "object based"", which is quite different

564 languages and perhaps object id's for unique objects. Object id's support the

568 object facility. Separate type system support is another extension.

569 [Booch 94, 2.2] proposes 7 "Elements of the Object Model"; 4 major and 3 minor:

579 1.16) Is A Class An Object? (Object-Oriented Technology)

586 1.17) Is An Object A Class? (Object-Oriented Technology)

590 systems, since any object may act as a class (provide object instantiation or

594 Behavior is how an object acts and reacts, in terms of its state changes

597 can access the internal state of an object of that class to perform some

599 the object to work on. This object is called the receiver, which is the object

664 than one object to be exposed. See [Kim ch 4, pp70-71 (D. Moon)] for an

691 point often mistaken in comp.object. E.g. simple statically

893 OOP package, naturalness (our "object concept"), resistance to change,

912 Polymorphism is the ability of an object (or reference) to assume (be replaced

913 by) or become many different forms of object. Inheritance (or delegation)

914 specifies slightly different or additional structure or behavior for an object,

915 and these more specific or additional attributes of an object of a base class

916 (or type) when assuming or becoming an object of a derived class characterizes

918 polymorphism, which allows an object (or reference) to assume or become any

919 object (possibly satisfying some implicit or explicit type constraints

959 Inclusion Polymorphism: an object can be viewed as belonging to many different

999 viewed in an almost symbolic way) occurs when object types may be specified and

1000 assignment is based on actual object membership in that type (often of the CLOS

1005 but lose the inherent type). Any object possessing all required operations is

1017 related by some common superclass; thus, any object denoted by this name is

1029 of an object can ever change. Only a reference can be polymorphic: ...".

1033 Self and Smalltalk, which allows an object (and not just a reference) to

1049 object (pointer or reference (or such parameter)) is assignment compatible with

1050 any object of a derived class. Is this polymorphism in itself? Objects

1054 respond in whatever way the object has defined (usually starting from its most

1058 for the polymorphic object; and hence, polymorphism. This common pure

1070 all such functions are resolved (statically) for actual objects. Formal object

1082 operation (along with parameters) to any object on the desktop, each of which

1083 handles the message in its own way (OO). If an (application) object can cut

1085 comes into play, as many overloaded cut methods, one per type of object to be

1086 cut, are available in the receiving object, the particular method being

1087 selected based on the actual type of object being cut (which in the GUI case is

1094 as each object knows what operation to support. It also allows a reduction in

1102 Yes (but be careful of context). To use C++ terminology, an object (not

1104 OO), called its most derived class. An object not directly contained in any

1105 other is called the complete object [Stroustrup 90]. An object is a member

1108 class, if a polymorphic object (or reference) is made to refer to an object,

1109 that object must be a member of the polymorphic object's class.

1155 but is of a different flavor (and usually requires object attributes by use.

1165 by providing object specialization. However, in many OO languages classes are

1166 used for assignment compatibility forcing an assigned object to inherit

1169 performed on any polymorphic object are satisfied by any replacing objects.

1173 from type, by the aforementioned definition of type), a replacing object must

1174 satisfy the operations or type constraints of a polymorphic object (subtype

1237 This refers to the usual class and object model. Its any 2+ level system

1245 to one of its base classes. In delegation systems, each object has a delegate

1247 on message passing where an object could delegate responsibility of a message

1249 object can be added to the delegate list, giving dynamic inheritance (of a

1255 object instantiation, or exemplars.

1266 Object Specialization [Sciore 89] is an example of a hybrid approach between

1268 of indirection and inheritance hierarchies are specified on a per object

1284 Object Pascal

1313 See also Appendices B and E and the comp.database.object newsgroup.

1317 structured subobjects, each object has its own identity, or object-id (as

1324 Another way of looking at Object-Oriented Databases is as a persistent object

1327 OODBs) that outlive the programs that create them. Object lifetimes can be

1331 having the longest. Persistent object stores do not support query or

1339 The Object Database Management Group (ODMG) has set up Gopher and Web

1346 information, updates to Release 1.1 of The Object Database Standard:

1367 GEOS (GeoWorks', written in Object Assembler, OO superset of 8086)

1389 Carrier principle, Object Directories

1432 Five Object Oriented Development Methods, Research report, HP Laboratories,

1435 oriented analysis methods. Journal of Object Oriented Programming (JOOP), pp

1455 Comparison of Object Oriented Analysis and Design Methodologies, Hawaii

1502 Object Management Group, Inc.

1504 The Object Management Group (OMG) is an international software industry

1511 In late 1990 the OMG published its Object Management Architecture

1519 1) the Object Request Broker, or key communications element, for

1522 2) the Object Model, or single design-portability abstract model for

1524 3) the Object Services, which will provide the main functions for

1525 realising basic object functionality using the Object Request Broker -

1538 In late 1991 OMG adopted its first interface technology, for the Object

1541 HyperDesk Corp., Digital Equipment Corp., Sun Microsystems and Object

1552 1) Object Oriented Databases;

1593 newsletter. First Class provides current information on Object

1595 Class offers an open editorial forum on numerous Object

1600 ongoing development of the Object Management Architecture are

1602 > Object Management Architecture Guide (OMA)

1613 > The Common Object Request Broker: Arch. and Spec. (Corba)

1614 The CORBA, as defined by the OMG's Object Request Broker (ORB),

1619 object systems. The Common Object Request Broker Architecture and

1630 o I would like to order ______ copy(s) of the Object Management

1654 Full implementation of the OMG CORBA 1.1 Object Request Broker. Also DOMF.

1664 > IBM SOM (System Object Model)

1669 Object RPC compatible with OMG CORBA 1.2 spec (will compile OMG IDL and

1677 > NCR 'Cooperative Frameworks' -- a Distributed Object Foundation

1680 > ORBELINE - The SMART Object Request Broker - PostModern Computing

1695 and Object Request Broker (ORB).

1711 something like an Object Broker, but it is *not* CORBA compatible (yet).

1725 HD-DOMS (HyperDesk Distributed Object Management System). A

1727 exercising objects, a bundled object database for persistent object

1758 specification from the Object Management Group with the DCE standard from

1773 HP ORB Plus consists of several components: the Distributed Object

1774 Management Facility (DOMF), object services, developers' and administrative

1782 System Object Model with extensions for distribution. This integration will

1790 "We're so convinced of the value of object technology that we're staking

1801 running distributed applications. These applications can use object

1814 object libraries;

1816 -- easier development, with remote object browsing so

1819 HP's DOMF includes the object request broker, interface- definition-

1849 Product: Isis Reliable Distributed Object Manager(tm) (RDOM)

1852 multi-lingual object-oriented applications. RDOM provides an "object group"

1867 Product: DOME - Distributed Object Management Environment

1869 Object Oriented Technologies Ltd,

1890 distributed object management; this allows the application to

1918 CORBA Implementation Descriptions: ORBELINE - The SMART Object Request Broker

1919 ORBeline is a complete implementation of OMG's Common Object Request

1935 The latest release of Orbix, Version 1.2, includes an Object Loader function

1939 of the Object Management Group's (OMG's) Common Object Request Broker

1941 distributed, object oriented applications following a consistent and

1944 at runtime through its Object Loader function. This enables developers to more

1946 traditional flat file databases, relational databases or object oriented

1959 IONA released Orbix for SunSoft Solaris and SunOS at the Object World

1964 Object World in London, England last October. Orbix for Microsoft Windows

2008 CORBA Implementation Descriptions: NCR 'Cooperative Frameworks' -- a Distributed Object Foundation

2014 a Distributed Object Foundation

2023 Cooperative Frameworks is a distributed object foundation

2032 - allows customers to build and use object services

2050 Cooperative Frameworks come with predefined object services

2053 provides object naming service

2060 - Persistence - the same object stream model for

2062 support object persistence. Persistent objects can be

2063 files, relational or object databases

2069 object activation when method invocations are required,

2089 object services can be implemented directly in C++)

2143 SUITESOFTWARE's Distributed Object Management Environment (DOME)

2160 Calls (RPC), Message-Oriented Middleware (MOM), and Object Request

2177 DOME allows message transfer from one object to another object,

2178 provides the ability to find an object, register an object, register

2179 the message interface to an object, and dynamically invoke an object.

2180 DOME also provides object services beyond the Object Request Broker

2270 "Distributed Object Computing With CORBA", C++ Report, July

2272 The Object Database Standard: ODMG-93

2296 3: An object which is responsible for deallocating storage must be

2297 certain that no other object still needs that storage. Thus many

2314 scheme each object keeps a count of references to it. When this count

2315 drops to zero the object is automatically deallocated. However this

2357 determine the last use of an object and provide deletion. This makes reuse

2376 of an object or the object itself. Programmers sometimes use reference

2383 object. While this is often possible in procedural languages, the object-

2386 of an object. For example, event driven GUI programs frequently have no

2436 Posted to comp.object, comp.lang.c++, comp.lang.smalltalk and

2510 Validation and Testing of Object Oriented Systems, BT Technol

2545 Love, Tom. Object Lessons. SIGS Books, 588 Broadway #604, New York, NY

2559 Object Oriented Systems, M.P.R Teltech Ltd. A poster at the

2560 Conference on Object Oriented Programming Systems, Languages

2587 Taylor, David. "A quality-first program for object technology", Object

object-oriented

8 Object-oriented programming has roots that can be traced to the 1960s. As hardware and software became increasingly complex, manageability often became a concern. Researchers studied ways to maintain software quality and developed object-oriented programming in part to address common problems by strongly emphasizing discrete, reusable units of programming logic[citation needed]. The technology focuses on data rather than processes, with programs composed of self-sufficient modules ("classes"), each instance of which ("objects") contains all the information needed to manipulate its own data structure ("members"). This is in contrast to the existing modular programming that had been dominant for many years that focused on the function of a module, rather than specifically the data, but equally provided for code reuse, and self-sufficient reusable units of programming logic, enabling collaboration through the use of linked modules (subroutines). This more conventional approach, which still persists, tends to consider data and behavior separately.

11 The Smalltalk language, which was developed at Xerox PARC (by Alan Kay and others) in the 1970s, introduced the term object-oriented programming to represent the pervasive use of objects and messages as the basis for computation. Smalltalk creators were influenced by the ideas introduced in Simula 67, but Smalltalk was designed to be a fully dynamic system in which classes could be created and modified dynamically rather than statically as in Simula 67.[9] Smalltalk and with it OOP were introduced to a wider audience by the August 1981 issue of Byte Magazine.

13 Object-oriented programming developed as the dominant programming methodology in the early and mid 1990s when programming languages supporting the techniques became widely available. These included Visual FoxPro 3.0, C++[citation needed], and Delphi[citation needed]. Its dominance was further enhanced by the rising popularity of graphical user interfaces, which rely heavily upon object-oriented programming techniques. An example of a closely related dynamic GUI library and OOP language can be found in the Cocoa frameworks on Mac OS X, written in Objective-C, an object-oriented, dynamic messaging extension to C based on Smalltalk. OOP toolkits also enhanced the popularity of event-driven programming (although this concept is not limited to OOP). Some[who?] feel that association with GUIs (real or perceived) was what propelled OOP into the programming mainstream.

15 Object-oriented features have been added to many existing languages during that time, including Ada, BASIC, Fortran, Pas cal, and others. Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code.

16 More recently, a number of languages have emerged that are primarily object-oriented yet compatible with procedural methodology, such as Python and Ruby. Probably the most commercially important recent object-oriented languages are Visual Basic.NET (VB.NET) and C#, both designed for Microsoft's .NET platform, and Java, developed by Sun Microsystems. Both frameworks show the benefit of using OOP by creating an abstraction from implementation in their own way. VB.NET and C# support cross-language inheritance, allowing classes defined in one language to subclass classes defined in the other language. Developers usually compile Java to bytecode, allowing Java to run on any operating system for which a Java virtual machine is available. VB.NET and C# make use of the Strategy pattern to accomplish cross-language inheritance, whereas Java makes use of the Adapter pattern[citation needed].

17 Just as procedural programming led to refinements of techniques such as structured programming, modern object-oriented software design methods include refinements[citation needed] such as the use of design patterns, design by contract, and modeling languages (such as UML).

20 Benjamin C. Pierce and some other researchers view as futile any attempt to distill OOP to a minimal set of features. He nonetheless identifies fundamental features that support the OOP programming style in most object-oriented languages:

27 Additional concepts used in object-oriented programming include:

34 There have been several attempts at formalizing the concepts used in object-oriented programming. The following concepts and constructs have been used as interpretations of OOP concepts:

39 Inheritance (object-oriented programming)

44 See also: List of object-oriented programming languages

55 Challenges of object-oriented design are addressed by several methodologies. Most common is known as the design patterns codified by Gamma et al.. More broadly, the term "design patterns" can be used to refer to any general, repeatable solution to a commonly occurring problem in software design. Some of these commonly occurring problems have implications and solutions particular to object-oriented development.

57 Design Patterns: Elements of Reusable Object-Oriented Software is an influential book published in 1995 by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, sometimes casually called the "Gang of Four". Along with exploring the capabilities and pitfalls of object-oriented programming, it describes 23 common programming problems and patterns for solving them. As of April 2007, the book was in its 36th printing.

63 Both object-oriented programming and relational database management systems (RDBMSs) are extremely common in software today. Since relational databases don't store objects directly (though some RDBMSs have object-oriented features to approximate this), there is a general need to bridge the two worlds. The problem of bridging object-oriented programming accesses and data patterns with relational databases is known as Object-Relational impedance mismatch. There are a number of approaches to cope with this problem, but no general solution without downsides.[20] One of the most common approaches is object-relational mapping, as found in libraries like Java Data Objects and Ruby on Rails' ActiveRecord.

65 OOP can be used to associate real-world objects and processes with digital counterparts. However, not everyone agrees that OOP facilitates direct real-world mapping (see Negative Criticism section) or that real-world mapping is even a worthy goal; Bertrand Meyer argues in Object-Oriented Software Construction that a program is not a model of the world but a model of some part of the world; "Reality is a cousin twice removed". At the same time, some principal limitations of OOP had been noted. For example, the Circle-ellipse problem is difficult to handle using OOP's concept of inheritance.

73 Luca Cardelli wrote a paper titled "Bad Engineering Properties of Object-Oriented Languages" Richard Stallman wrote in 1995, "Adding OOP to Emacs is not clearly an improvement; I used OOP when working on the Lisp Machine window systems, and I disagree with the usual view that it is a superior way to program."

78 Joe Armstrong, the principal inventor of Erlang, is quoted as saying "The problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle."

82 Carnegie-Mellon University Professor Robert Harper in March 2011 wrote: "This semester Dan Licata and I are co-teaching a new course on functional programming for first-year prospective CS majors... Object-oriented programming is eliminated entirely from the introductory curriculum, because it is both anti-modular and anti-parallel by its very nature, and hence unsuitable for a modern CS curriculum. A proposed new course on object- oriented design methodology will be offered at the sophomore level for those students who wish to study this topic."

193 classical object-oriented languages associate method, field and parent

227 1.2) What Is Object Encapsulation (Or Protection)? (Object-Oriented Technology)

242 However most object-oriented languages provide a well defined interface to

267 1.3 What Is A Class? (Object-Oriented Technology)

269 in object-oriented methods. Within the OO context, a class is a specification

295 1.4) What Is A Meta-Class? (Object-Oriented Technology)

341 1.5) What Is The Infinite Regress Of Objects And Classes? (Object-Oriented Technology)

348 1.6) What Are MOPs And Reflection? (Object-Oriented Technology)

360 of object-oriented reuse, since the compiler itself is reused thru

366 1.7) What Is Inheritance? (Object-Oriented Technology)

423 1.8) What Is Multiple Inheritance? (Object-Oriented Technology)

434 1.9) Does Multiple Inheritance Pose Any Additional Difficulties? (Object-Oriented Technology)

447 object-oriented programming, because many objects in the real world belong to

451 1.10) What Is Dynamic Inheritance? (Object-Oriented Technology)

464 1.11) What Is Shared (Repeated) Inheritance? (Object-Oriented Technology)

477 1.12) Why Use Inheritance? (Object-Oriented Technology)

506 Why Don't Some People Like Inheritance? (Object-Oriented Technology)

508 object-oriented languages provide). They would also like to see more

529 Overriding? (Object-Oriented Technology)

541 1.15) What Is The Difference Between Object-Based And Object-Oriented? (Object-Oriented Technology)

546 both inheritance and polymorphism and are object-oriented. [Cardelli 85, p481]

547 state "that a language is object-oriented if and only if it satisfies the

553 object-oriented = data abstractions + object types + type inheritance

556 Object-Oriented = Classes and Objects

563 A more modern definition of "object-oriented" includes single-hierarchy

579 1.16) Is A Class An Object? (Object-Oriented Technology)

586 1.17) Is An Object A Class? (Object-Oriented Technology)

592 1.18) What Is A Method? (And Receiver And Message) (Object-Oriented Technology)

614 What Are Multi-Methods And Multiple-Polymorphism? (Object-Oriented Technology)

636 also the true essence of object-oriented polymorphism, which allows objects to

694 1.20) What Is OOP? (Object-Oriented Technology)

695 OOP stands for Object-Oriented Programming, the usual programming

701 OOD (And Where Can I Get What I Need On It)? (Object-Oriented Technology)

739 Object-oriented domain analysis (OODA) seeks to identify reusable items

743 OOA and OOD stand for Object-Oriented Analysis and Object-Oriented Design,

744 respectively. OOA strives to understand and model, in terms of object-oriented

871 Object-oriented analysis now includes "Enterprise Modeling" [Martin 92], also

877 1.22) Where Did Object-Orientation Come From? (Object-Oriented Technology)

878 Simula was the first object-oriented language providing objects, classes,

880 It was intended as a conveyance of object-oriented design. Simula 1 was a

888 1.23) What Are The Benefits Of Object-Orientation? (Object-Oriented Technology)

897 and procedures (top-down) are frequently changed, providing object-oriented

899 2.1) What Is Polymorphism? (Typing - Object-Oriented Technology)

900 Polymorphism is a ubiquitous concept in object-oriented programming and is

917 object-oriented polymorphism. This is a special case of parametric

1023 "Polymorphism" means the ability to take several forms. In object-oriented

1047 2.2) What Does Polymorphism Boil Down To In OO Programming Languages? (Typing - Object-Oriented Technology)

1063 2.3) What Is Dynamic Binding? (Typing - Object-Oriented Technology)

1101 2.4) Is There A Difference Between Being A Member Or Instance Of A Class? (Typing - Object-Oriented Technology)

1113 2.5) What Is The Difference Between Static And Dynamic Typing? (Typing - Object-Oriented Technology)

1134 2.6) What Is This I Hear About ML And Functional Programming Languages? (Typing - Object-Oriented Technology)

1151 2.7) What Is A Separation Between Type And Class (Representation)? (Typing - Object-Oriented Technology)

1207 2.8) What Are Generics And Templates? (Typing - Object-Oriented Technology)

1236 3.1) What Is The "Classical" Object-Oriented Paradigm?

1240 Prototyping" Object-Oriented Paradigm?

1258 3.3) Are There Any Other Object-Oriented Paradigms?

1271 3.4) What Are The Major Object-Oriented Programming Languages Today?

1312 3.5) What Are Object-Oriented Databases And Persistence?

1315 Object-Oriented Databases are databases that support objects and classes. They

1320 object-oriented database. OODBs allow all the benefits of object-orientation,

1321 as well as the ability to have a strong equivalence with object-oriented

1324 Another way of looking at Object-Oriented Databases is as a persistent object

1333 Appendix B also contains references for object-oriented interfaces to

1354 3.6) What Are Object-Oriented Operating Systems?

1356 Object-Oriented Operating Systems provide resources through objects, sometimes

1386 This thesis covers the design of an extensible object-oriented

1397 3.7) What Are The Current Object-Oriented Methodologies?

1440 Fichman, Robert and Kemerer, Chris. Object-Oriented and Conventional Analysis

1449 A Comparison of Six Object-oriented Analysis and Design Methods. Report

1461 Monarchi, David and Puhr, Gretchen I. A Research Typology for Object-Oriented

1470 Booch, G. - Object-oriented analysis and design with applications, 1994.

1471 Champeaux, D. de - Object-oriented system development, 1993.

1472 Coad, P., and Yourdon, E. - Object-oriented analysis (2nd edition), 1991a.

1473 Coad, P., and Yourdon, E. - Object-oriented design, 1991b.

1474 Coleman, D. - Object-oriented development, the Fusion method, 1994.

1475 Henderson-Sellers, B. and Edwards, J.M. - Methodology for Object-oriented

1478 Jacobson, I. - Object-oriented software engineering, 1993.

1479 Martin, J., Odell, J. - Object-oriented analysis and design, 1992.

1480 Martin, J., Odell, J. - Principles of object-oriented analysis and design,

1482 Rumbaugh, J. et.al. - Object-oriented modeling and design, 1991.

1483 Shlaer, S., Mellor, S.J. - Object-oriented systems analysis: Modeling the

1485 Wirfs-Brock, R. et.al. - Designing object-oriented software, 1990.

1496 CORBA - Object-Oriented Technology)

1506 (*) promotion of the object-oriented approach to software engineering

1510 processing) using object-oriented methodology.

1513 object-oriented languages, systems, databases and application

1514 frameworks; an abstract framework for object-oriented systems; a set

1516 (reference model) for distributed applications using object-oriented

1523 communicating with OMG-conforming object-oriented systems;

1548 In order to serve OMG membership interested in other object-oriented systems

1566 CORBA - Object-Oriented Technology)

1609 that the object-oriented approach to software construction best

1638 CORBA - Object-Oriented Technology)

1692 - an open system, standards compliance, object-oriented architecture,

1739 SCALABLE, OBJECT-ORIENTED APPLICATIONS

1743 object-oriented applications.

1786 "plug-and-play" object-oriented environment. This will give developers,

1822 writing distributed, object-oriented applications require additional

1852 multi-lingual object-oriented applications. RDOM provides an "object group"

1866 CORBA Implementation Descriptions: Object-Oriented Technologies DOME

2046 - building next-generation, object-oriented,

2157 - object-oriented architecture

2188 o Object-Oriented Architecture

2189 Because DOME's architecture is object-oriented, there are significant

2268 CORBA - Object-Oriented Technology)

2276 3.9) Why is Garbage Collection A Good Thing? (Object-Oriented Technology)

2279 company on the necessity of garbage collection for object-oriented programming

2327 [1] "Object-Oriented Software Construction" by Meyer puts the argument

2349 3.9b) Why is Garbage Collection Necessary for Object-Oriented Programming? (Object-Oriented Technology)

2353 There are several reasons why true object-oriented programming requires garbage

2371 Implementation hiding is a pillar of object-oriented programming,

2413 mature technology.[1] Many object-oriented languages specify garbage

2426 object-oriented programmer's toolbox.

2427 3.10) What Can I Do To Teach OO To The Kids? (Object-Oriented Technology)

2432 3.11) What Is Available On Object-Oriented Testing?

2434 Testing of Object-Oriented Programming (TOOP) FAQ

2442 This is a summary of resources on the Testing of Object-Oriented

2459 I am NOT a researcher on the testing of object-oriented programming.

2478 3.11) What Is Available On Object-Oriented Testing? Written Material

2479 Berard, Edward. Essays on Object-Oriented Software Engineering.

2481 This book has two chapters on testing of object-oriented software,

2494 Cheatham Thomas J., and Lee Mellinger, "Testing Object-Oriented

2498 Object-Oriented Programs", Proceedings of the 4th Symposium on

2501 Fiedler, Steven P., "Object-Oriented Unit Testing", Hewlett-Packard

2503 Firesmith, D.G., "Testing Object-Oriented Software", Proceedings

2506 Object-Oriented Programs", Proceedings of the 8th Pacific

2514 "Incremental Testing of Object-Oriented Class Structures",

2544 Object-Oriented Programs", IEEE Software, July 1991, pp. 72-80.

2551 Makes the argument that testing of object-oriented software is

2563 Murphy, G. and P. Wong. Object-Oriented Systems Testing Methodology: An

2566 Perry, D.E. and G.E. Kaiser, "Adequate Testing and Object-Oriented

2567 Programming", Journal of Object-Oriented Programming,

2571 object-oriented programming", Journal of Object-Oriented

2573 Smith, M. D. and D. J. Robson, " A Framework for Testing Object-Oriented

2576 could be adapted for object-oriented software.

2583 Smith, M. D. and D. J. Robson, "Object-Oriented Programming - the

2593 Turner, C. D. and D. J. Robson, "The Testing of Object-Oriented Programs",

2606 Testing of Object-Oriented Programs", Technical Report

2641 3.11) What Is Available On Object-Oriented Testing? Software

objects

28 Classes of objects

30 Methods which act on the attached objects.

40 records are basis for understanding objects if function literals can be stored in fields (like in functional programming languages), but the actual calculi need be considerably more complex to incorporate essential features of OOP. Several extensions of System F<: that deal with mutable objects have been studied;[18] these allow both subtype polymorphism and parametric polymorphism (generics)

49 Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original form. Examples: Oberon (Oberon-1 or Oberon-2) and Common Lisp.

67 Steve Yegge and others noted that natural languages lack the OOP approach of strictly prioritizing things (objects

85 similar objects are defined in their common class; the terms instance and

91 objects typically existed in Simula programs to simulate some aspect of

100 to certain objects in our awareness". [Rumbaugh 91] defines: "We define an

107 and on identifying objects: "What are the *things* in this problem? Most of

110 covers "Identifying Key Abstractions" for objects and classes based on an

112 to identifying objects through use-cases (scenarios), leading to a use-case

115 Ordinary Objects - Typical OOPL objects

116 Use-Cases and Actors - Actors <--> Use-Cases <--> Object Model Objects

117 Megaobjects - Composite objects (~ subsystems with inheritance)

120 Application Objects - In the Object Model

123 Entity - Correspond to real-world objects

124 Component Objects - Utility and Implementation hiding objects

133 The implementation of objects could roughly be categorized into descriptor-

140 objects [Kim 89, ch 19 and Yaoqing 93]. Simple static approaches are found in

146 have no type, but the objects (values) they point to always do. An untyped

154 Simple statically-typed objects (static and auto vars and temps in C++ and

191 only objects, they are referred to as single-hierarchy, or 1 Level systems.

192 Objects contain fields, methods and delegates (pseudo parents), whereas

194 definitions with classes (and only associate state and class with objects,

196 However, one-le vel objects often play the role of classes to take advantage of

198 or shared state, otherwise idiosyncratic objects, a powerful and natural

199 concept, will result. Typical 1 Level objects can contain any number of

213 window and icon objects display different behavior (although cognitive

222 as collections of objects view, which is the same as the types as sets of

235 Some languages permit arbitrary access to objects and allow methods to be

237 Object Pascal provide no protection for objects, meaning instance variables

243 their objects thru classes. C++ has a very general encapsulation

271 (parents, or recursive structure and behavior) for objects. As pointed out

276 objects (as opposed to a collection of objects, as with the more classical

279 objects:

285 "A class is a set of objects that share a common structure and a common

309 All objects can be viewed as classes and all classes can be viewed as

310 objects (as in Self). There is no need for Meta-Classes because objects

314 All Objects are instances of a Class but Classes are not accessible to

317 There are 2 kinds of distinct objects: objects and classes.

319 All objects are instances of a class and all classes are instances of

323 be first class objects and therefore classes are available to programs.

324 There are 2 kinds of distinct objects (objects and classes), with a

339 C++). There are 3 distinct kinds of objects (objects, classes, and

341 1.5) What Is The Infinite Regress Of Objects And Classes? (Object-Oriented Technology)

358 differentially without affecting them and their extant objects. Thus, many

367 Inheritance provides a natural classification for kinds of objects and allows

368 for the commonality of objects to be explicitly taken advantage of in modeling

381 In delegation languages, such as Self, inheritance is delegation where objects

382 refer to other objects to respond to messages (environment) and do not

447 object-oriented programming, because many objects in the real world belong to

452 Dynamic inheritance allows objects to change and evolve over time. Since base

453 classes provide properties and attributes for objects, changing base classes

458 or change parents from objects (or classes) at run-time. Actors, CLOS, and

503 the static class, as in C++ slicing). Maintaining the dynamic type of objects

542 Object-Based Programming usually refers to objects without inheritance

549 - It supports objects that are data abstractions with an interface of named

551 - Objects have an associated type.

556 Object-Oriented = Classes and Objects

564 languages and perhaps object id's for unique objects. Object id's support the

565 modern notion of relocatable, persistent and distributed objects that can

566 even migrate across machines. Distributed Smalltalk's proxy objects [Kim 89,

582 are objects in 3 Level Systems and above because classes are instances of

583 meta-classes. But classes play a dual role, because objects can only be

584 declared to be instances of a class (and class objects instances of a

585 meta-class). In 1 Level (single-hierarchy) systems, all classes are objects.

588 Classes. Instances of a Class (ordinary objects) are not classes (excluding

589 hybrid systems). However, all objects may be classes in single hierarchy

636 also the true essence of object-oriented polymorphism, which allows objects to

648 the actual classes of objects present:

706 "In OOA, we seek to model the world by identifying the classes and objects

722 analysis seeks to identify the classes and objects that are common to all

726 operations, objects, and structures that commonly occur in software systems

740 localized around objects, e.g., classes, instances, systems of interacting

741 objects, and kits [frameworks]. OORA analysts and OOD designers will

745 concepts (objects and classes), a particular problem within a problem domain

766 "structured" techniques, with greater emphasis on objects. OOram [Reenskaug

814 Since classes and objects are used in all phases of the OO software life-cycle,

878 Simula was the first object-oriented language providing objects, classes,

896 On resistance to change, system objects change infrequently while processes

924 many uses in the sciences, all referring to objects that can take on or assume

984 classes as sets of objects (resulting in subtype objects are a subset of

985 supertype objects, or an extensional view), as contrasted with a feature based

1016 variable declaration) may denote objects of many different classes that are

1050 any object of a derived class. Is this polymorphism in itself? Objects

1051 can take on objects of different forms (the derived classes), but of what use

1053 dynamically typed languages, polymorphic objects are passed messages and will

1055 derived class and working its way up). But for static objects, a virtual

1070 all such functions are resolved (statically) for actual objects. Formal object

1072 vtables of function pointers in the actual objects (C++) or equivalent,

1084 many kinds of objects such as text and graphical objects, multiple-polymorphism

1091 Dynamic binding allows new objects and code to be interfaced with or added to

1115 information is available on objects at run-time. Dynamic typing uses the

1116 inherent types of polymorphic objects, keeping track of the types of objects at

1126 cases) to be available on formal objects and a lack of multiple-polymorphism

1169 performed on any polymorphic object are satisfied by any replacing objects.

1189 This helps to insure the semantic integrity of replacing objects and their

1248 it couldn't handle to objects that potentially could (its delegates). Any

1251 inheritance" in which fields and methods can be added and deleted from objects.

1252 This makes for easy "prototyping", which allows for objects to be constructed

1254 delegation languages usually refers to objects serving as prototypes for

1273 Add 1 To Cobol giving Cobol with Objects.

1315 Object-Oriented Databases are databases that support objects and classes. They

1326 Persistence is often defined as objects (and their classes in the case of

1330 lifetime and objects stored indefinitely in an OODB (which are persistent)

1356 Object-Oriented Operating Systems provide resources through objects, sometimes

1358 They are almost always distributed systems (DOS or DPOS), allowing objects to

1360 objects, and hence system resources, can only be accessed if a capability to

1520 handling distribution of messages between application objects in

1526 the logical modeling and physical storage of objects; and

1615 provides the mechanisms by which objects transparently make

1727 exercising objects, a bundled object database for persistent object

1764 operating systems, networking protocols or where application objects are

1770 standard for how objects (in applications, repositories or class libraries)

1803 storage mechanism to facilitate the reuse of objects.

1817 developers can find and use objects more quickly.

1823 interfaces to use objects effectively. So developers don't need to create

1831 interoperability is planned so objects written in different languages can be

1854 cooperating objects. RDOM is built on top of the Isis Distributed

1943 With Orbix Version 1.2 IONA has added the ability to dynamically load objects

1950 populated with all objects or services available at runtime keeping programmers

1951 informed of the functions, attributes and characteristics of objects and

1968 Windows 3.1 and SunSoft's Distributed Objects Everywhere (DOE) on Solaris.

2057 designed around fine grained objects, developers can

2058 build distributed objects as large or as small as

2062 support object persistence. Persistent objects can be

2283 language which will automatically reclaim objects which are no longer used.

2303 and comparing whole objects rather than just references. This is a

2360 about the rest of the program to determine ownership of the objects in the

2366 objects, lack of polymorphism, and problems with interior pointers (e.g.

2384 oriented paradigm of objects sending messages to each other (possibly from

2401 c) Value semantics store objects rather than references, inhibiting data

2402 sharing and carrying expensive performance costs when complex objects are

2430 objects was something more intuitive and natural than coding procedures.

2645 specific classes that test non-interactive objects such as trees,

class

71 Responsibility-driven design defines classes in terms of a contract, that is, a class should be defined around a responsibility and the information that it shares. This is contrasted by Wirfs-Brock and Wilkerson with data-driven design, where classes are defined around the data-structures that must be held. The authors hold that responsibility-driven design is preferable.

85 similar objects are defined in their common class; the terms instance and

157 (C++). The record (class) may also contain operations which are called

165 A virtual member in statically typed languages is a base class member that can

166 be set or respecified by a derived class. This is roughly equivalent to a

167 pointer or function pointer in the base class being set by the derived class.

180 derived class, parent class

181 base class, and etc. will be used interchangeably.

183 derived class terminology

190 languages. Since there is no separate class construct in these languages, and

194 definitions with classes (and only associate state and class with objects,

202 thus performing the classical role of a class. In typical prototyping systems,

236 defined outside of a class as in conventional programming. Simula and

239 outside of a class, providing functions and procedures. While both CLOS

248 a class. A Stack's representation, such as a list or array, will usually be

249 private. Protected members are accessible from within a class and also from

252 class to specify friends (other (sub)classes and functions), that can access

255 For another example, Smalltalk's class instance variables are not accessible

256 from outside of their class (they are not only private, but invisible).

259 class. All Smalltalk instance variables can be accessed by subclasses,

262 is most common (e.g. Ada, C++, Eiffel), where class methods can access any

263 object of that class and not just the receiver. Methods can only access the

267 1.3 What Is A Class? (Object-Oriented Technology)

268 A class is a general term denoting classification and also has a new meaning

269 in object-oriented methods. Within the OO context, a class is a specification

274 intensional definition, emphasizing a class as a descriptor

278 Original Aristotlean classification defines a "class" as a generalization of

285 "A class is a set of objects that share a common structure and a common

286 behavior." "A single object is simply an instance of a class."

287 The intension of a class is its semantics and its extension is its instances

297 A Meta-Class is a class' class. If a class is an object, then that object

298 must have a class (in classical OO anyway). Compilers provide an easy way to

301 the work of being a class. This can be declared in a class named "Meta-Class".

314 All Objects are instances of a Class but Classes are not accessible to

319 All objects are instances of a class and all classes are instances of

320 Meta-Class. The Meta-Class is a class and is therefore an instance of

323 be first class objects and therefore classes are available to programs.

325 distinguished class, the metaclass.

329 a 3 Level System, but as a class it also has a specialized Meta-Class, the

330 "Meta-Class class" and this results in a 5 Level System:

332 class

333 class class (Smalltalk's Meta-Classes)

335 Meta-Class class

336 The "class class"es handle messages to classes, such as constructors and

337 "new", and also "class variables" (a term from Smalltalk), which are

338 variables shared between all instances of a class (static member data in

343 class (Meta-Object), a class is an instance of a Meta-Class, which must also

347 class" instance-of loop (as in Smalltalk).

352 what is this object's class, give info on this class, etc.) and an

354 modification (e.g. add the following method or instance to this class,

372 Inheritance is a relationship between classes where one class is the parent

376 etc.) class of another. Inheritance provides

388 inheritance can also share parents within a class lattice (CLOS and Eiffel

399 Inheritance can also be used for typing, where a type or class can be used to

405 used synonymously, but can be used to show the "object is-a class"

416 Class hierarchies are subjective [Booch 91, 4.2; Lakoff 87] and usually drawn

417 with the parent class on top, but more demanding graphs (as is often the case

419 base class and the tail indicating the derived class.

421 by making a small change to a class. Creating a subclass to alter a method

422 or to add a method to a parent class is an example.

424 Multiple Inheritance occurs when a class inherits from more than one parent.

427 Mixin's is a style of MI (from flavors) where a class is created to provide

429 inherited by any class requiring them. Method combination, or calling

432 explicitly calling them, allowing client class code to remain unchanged [Booch

435 Yes, it does. Any name can be simply resolved to a class member with single

444 class qualifier can be used to explicitly disambiguate. Smalltalk renders

448 several classes. In classical systems without MI, a class which should inherit

449 from more than one class must textually include all but one of those classes in

454 changes the properties and attributes of a class. A previous example was a

456 base class between a window and icon class.

465 Multiple Inheritance brings up the possibility for a class to appear as a

466 parent more than once in a class graph (repeated inheritance), and there is

467 then a potential to share that class. Only one instance of the class will

471 specified as virtual (virtual bases) are shared within the same class lattice,

484 class diagram, all routines and structure available in class Computer are

487 of reuse takes advantage of the is-a-kind-of relationship. Class libraries

492 With differential programming, a class does not have to be modified if it is

493 close to what's required; a derived class can be created to specialize it.

497 CLOS, Eiffel, etc.) based on inheritance when type and class are bound together

499 which is a member of (inherits from) a class is polymorphically assignment

501 class. Such assignment can result in the loss of an object's dynamic type in

503 the static class, as in C++ slicing). Maintaining the dynamic type of objects

533 (virtual in Simula and C++) method in a derived class, thus providing

535 "frozen" features in Eiffel can be "redefined" in a derived class. Whenever

536 a method is invoked on an object of the base class, the derived class method

537 is executed overriding the base class method, if any. Overriding in Simula

579 1.16) Is A Class An Object? (Object-Oriented Technology)

580 In C++ no, because C++ classes are not instances of an accessible class (a

584 declared to be instances of a class (and class objects instances of a

586 1.17) Is An Object A Class? (Object-Oriented Technology)

588 Classes. Instances of a Class (ordinary objects) are not classes (excluding

590 systems, since any object may act as a class (provide object instantiation or

596 A method is a function or procedure which is defined in a class and typically

597 can access the internal state of an object of that class to perform some

674 parameters but limiting base class usage (as in Eiffel). If these restrictions

676 declared in a base class may have several functions overriding it in a derived

677 class differentiated only by their formal argument types. This therefore

915 and these more specific or additional attributes of an object of a base class

916 (or type) when assuming or becoming an object of a derived class characterizes

1034 change its class.]

1050 any object of a derived class. Is this polymorphism in itself? Objects

1055 derived class and working its way up). But for static objects, a virtual

1056 function is invoked. This is the stored method from the derived class that

1057 overrode the virtual method from its base class, providing specialized behavior

1067 function at run-time because a derived class may override the function, in

1074 function pointers with static typechecking in the base class, and filling them

1075 in in the derived class, along with offsets to reset the receiver).

1101 2.4) Is There A Difference Between Being A Member Or Instance Of A Class? (Typing - Object-Oriented Technology)

1103 a reference) is defined to be an instance of exactly one class (in classical

1104 OO), called its most derived class. An object not directly contained in any

1107 class inherits from. With static typing and inclusion polymorphism based on

1108 class, if a polymorphic object (or reference) is made to refer to an object,

1109 that object must be a member of the polymorphic object's class.

1112 a class is one of its instance variables in C++.

1124 restrictions include only allowing a common set of base class functions (or

1151 2.7) What Is A Separation Between Type And Class (Representation)? (Typing - Object-Oriented Technology)

1167 (transitively) from any polymorphic object's class (inclusion polymorphism

1168 based on class, or subclass polymorphism). This insures all operations to be

1172 By separating type from class, or representation (or perhaps separating class

1217 parameterized base type. This allows a single Stack class to provide

1237 This refers to the usual class and object model. Its any 2+ level system

1244 derived class does not have a desired attribute, it "delegates" responsibility

1269 class

1529 compliant class interfaces.

1558 7) Class Libraries.

1591 > First Class (Bi-Monthly Newsletter)

1592 First Class is OMG's non-commercial bi-monthly 28-page

1593 newsletter. First Class provides current information on Object

1595 Class offers an open editorial forum on numerous Object

1628 o I would like a one year subscription to First Class

1770 standard for how objects (in applications, repositories or class libraries)

1894 DOME is constructed as a C++ class library, from which ORBs

2027 C++ class libraries that:

2056 - Fine-grain Data Management - class libraries are

2470 must be shipped with the class libraries.

2471 As soon as one major class library vendor starts to ship real test code

2474 about it. If you had to recommend a class library to a committee that

2476 safer with a class library that could be auto-tested in your

2514 "Incremental Testing of Object-Oriented Class Structures",

2517 Hoffman, Daniel and Paul Strooper. A Case Study in Class Testing.

2522 example is worked out in C++ which tests a commercial class.

2525 Hoffman, D.M. and P.A. Strooper. Graph-Based Class Testing. In

2549 during the first release of their initial class library.

2622 methods of making class declarations and the implications of

2639 Wong, P. Automated Class Exerciser (ACE) User's Guide. Technical

2642 There is a smalltalk class library in the Univ. of Illinois archives

2643 which includes a simple Tester class written by Bruce Samuelson

2688 MicroTech Pacific Research (mpr.ca) has a C++ class testing tool called

2689 ACE (Automated Class Exerciser) which is available under non-disclosure

classes

28 Classes of objects

29 Instances of classes

49 Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original form. Examples: Oberon (Oberon-1 or Oberon-2) and Common Lisp.

87 defined in [Coplien 92, p280], where "classes play a central role in the

110 covers "Identifying Key Abstractions" for objects and classes based on an

119 Patterns** (Typical) - Framework-like, crsp. classes and comm patterns only

162 roughly equivalent to a loosely coupled variant record, with derived classes

189 flexible kind of object which can play the role of classes in classical OO

194 definitions with classes (and only associate state and class with objects,

196 However, one-le vel objects often play the role of classes to take advantage of

218 Chambers has proposed an interesting variation called "Predicate Classes"

219 [Chambers 93] as a part of his Cecil language. These classes will only be

221 classes

243 their objects thru classes. C++ has a very general encapsulation

250 within subclasses (also called derived classes). A Stack's representation

252 class to specify friends (other (sub)classes and functions), that can access

254 specific classes.

260 helping with abstract classes and overriding.

272 above, classes can also specify access permissions for clients and derived

273 classes, visibility and member lookup resolution. This is a feature-based or

299 picture Meta-Classes. Classes must be implemented in some way; perhaps with

309 All objects can be viewed as classes and all classes can be viewed as

314 All Objects are instances of a Class but Classes are not accessible to

317 There are 2 kinds of distinct objects: objects and classes.

319 All objects are instances of a class and all classes are instances of

322 2 Level System). This allows classes to

323 be first class objects and therefore classes are available to programs.

324 There are 2 kinds of distinct objects (objects and classes), with a

328 of specialized Meta-Classes for classes. There is still a Meta-Class as in

336 The "class class"es handle messages to classes, such as constructors and

339 C++). There are 3 distinct kinds of objects (objects, classes, and

341 1.5) What Is The Infinite Regress Of Objects And Classes? (Object-Oriented Technology)

372 Inheritance is a relationship between classes where one class is the parent

407 between classes only. In one-level systems, is-a (object instantiation) and

420 Differential programming is the use of inheritance to reuse existing classes

428 additional attributes or properties to other classes. They are intended to be

440 which to choose becomes an issue. Eiffel forces derived classes to rename

448 several classes. In classical systems without MI, a class which should inherit

449 from more than one class must textually include all but one of those classes in

453 classes provide properties and attributes for objects, changing base classes

458 or change parents from objects (or classes) at run-time. Actors, CLOS, and

481 the world by using classes and concepts for generalization and categorization,

490 as library classes have already been tested and further use provides further

513 inheritance stuctures). Some don't like the coupling of classes (as in Jade),

531 derived classes into a common base (or parent) is generalization [Booch 91,

544 These languages support abstract data types (Adts) and not classes, which

556 Object-Oriented = Classes and Objects

580 In C++ no, because C++ classes are not instances of an accessible class (a

581 Meta-Class) and because C++ classes are not accessible to programs. Classes

582 are objects in 3 Level Systems and above because classes are instances of

583 meta-classes. But classes play a dual role, because objects can only be

585 meta-class). In 1 Level (single-hierarchy) systems, all classes are objects.

588 Classes. Instances of a Class (ordinary objects) are not classes (excluding

589 hybrid systems). However, all objects may be classes in single hierarchy

648 the actual classes of objects present:

706 "In OOA, we seek to model the world by identifying the classes and objects

722 analysis seeks to identify the classes and objects that are common to all

740 localized around objects, e.g., classes, instances, systems of interacting

745 concepts (objects and classes), a particular problem within a problem domain

814 Since classes and objects are used in all phases of the OO software life-cycle,

878 Simula was the first object-oriented language providing objects, classes,

883 including classes, inheritance, a high-powered graphical environment and a

921 provided by base classes or types (subclass and subtype polymorphism,

960 classes that need not be disjoint; that is, there may be inclusion of

961 classes.

978 uses inclusion polymorphism; its used in declaring classes, and subclass

984 classes as sets of objects (resulting in subtype objects are a subset of

995 more than required. Since derived classes can inherit structure and behavior

996 from base classes, such inheritance is an example of inclusion polymorphism

1016 variable declaration) may denote objects of many different classes that are

1025 instances of various classes. In a typed environment such as Eiffel, this is

1036 The use of derived classes and virtual functions is often called "object-

1046 different classes.

1051 can take on objects of different forms (the derived classes), but of what use

1093 This removes the spread of knowledge of specific classes throughout a system,

1106 of several classes, including all of the classes its declared (or most derived)

1159 types (classes in OO) can be separated from the notion of type allowing many

1165 by providing object specialization. However, in many OO languages classes are

1191 Abstract classes ([Stroustrup 91] and [Meyer 88]) in typing provide a facility

1192 similar to subtype polymorphism; however, ACs require type compatible classes

1195 spreading knowledge of classes throughout a system, which is a high priority

1211 and functions with types. This is useful for parameterized classes and

1214 Generics are orthogonal to inheritance, since types (and classes)

1245 to one of its base classes. In delegation systems, each object has a delegate

1264 CLOS [Kim 89, ch 4] has a looser coupling of methods to classes and doesn't

1267 delegation and classical systems, where parent classes have an extra level

1315 Object-Oriented Databases are databases that support objects and classes. They

1326 Persistence is often defined as objects (and their classes in the case of

1678 (1) C++ ORB toolkit consisting of over 300 C++ classes and runtime libraries

1729 set of base classes to speed development, and a test script language.

1896 environment. This provides great flexibility since new classes

2030 distributed implementations of C++ classes over

2039 (1) C++ ORB toolkit consisting of over 300 C++ classes and

2464 Why is this important? If classes are really to be reused in

2465 confidence, they must be blatantly correct. The classes must be easily

2645 specific classes that test non-interactive objects such as trees,

2648 includes Tree classes, Tester itself, and subclasses of Tester that are

2649 used to validate the Tree classes. For ParcPlace Smalltalk (ObjectWorks

programming

26 Similarly, in his 2003 book, Concepts in programming languages, John C. Mitchell identifies four main features: dynamic dispatch, abstraction, subtype polymorphism, and inheritance.Michael Lee Scott in Programming Language Pragmatics considers only encapsulation, inheritance and dynamic dispatch.[16]

27 Additional concepts used in object-oriented programming include:

34 There have been several attempts at formalizing the concepts used in object-oriented programming. The following concepts and constructs have been used as interpretations of OOP concepts:

39 Inheritance (object-oriented programming)

44 See also: List of object-oriented programming languages

47 Languages designed mainly for OO programming, but with some procedural elements. Examples: C++, C#, VB.NET, Java, Python.

69 verbs).] This problem may cause OOP to suffer more convoluted solutions than procedural programming.

149 programming (see sections 2.3, 4.3, and [Coplien 92]).

172 and program complexity (fewer nested programming constructs) and allowing

236 defined outside of a class as in conventional programming. Simula and

377 programming by extension (as opposed to programming by reinvention

379 for differential programming. Inheritance can also double for assignment

420 Differential programming is the use of inheritance to reuse existing classes

447 object-oriented programming, because many objects in the real world belong to

492 With differential programming, a class does not have to be modified if it is

542 Object-Based Programming usually refers to objects without inheritance

561 programming often referred to as "object based"", which is quite different

657 real-world programming situations, unnecessarily. In the author's opinion,

671 efficiency, and to support a static programming idiom, but require restrictions

695 OOP stands for Object-Oriented Programming, the usual programming

800 Programming

804 Programming, prototyping, risk management

809 A little programming

818 programming gaps found in traditional structured analysis and design.

900 Polymorphism is a ubiquitous concept in object-oriented programming and is

1024 programming, this refers to the ability of an entity to refer at run-time to

1037 oriented programming". Furthermore, the ability to call a variety of

1047 2.2) What Does Polymorphism Boil Down To In OO Programming Languages? (Typing - Object-Oriented Technology)

1079 programming and user interaction (e.g. GUIs). Examples can be found in

1134 2.6) What Is This I Hear About ML And Functional Programming Languages? (Typing - Object-Oriented Technology)

1135 ML, Metalanguage, is a functional programming language with a strongly typed

1158 values. This can insure type-safe programming. However, the representation of

1196 for loosely coupled modules and in distributed programming [Black 87].

1216 programming languages. An example is a Stack with a generically

1271 3.4) What Are The Major Object-Oriented Programming Languages Today?

1391 It covers extensible objected-oriented programming from hardware up.

1435 oriented analysis methods. Journal of Object Oriented Programming (JOOP), pp

1829 cycle. The initial version will work with the C++ programming language.

2279 company on the necessity of garbage collection for object-oriented programming

2349 3.9b) Why is Garbage Collection Necessary for Object-Oriented Programming? (Object-Oriented Technology)

2353 There are several reasons why true object-oriented programming requires garbage

2371 Implementation hiding is a pillar of object-oriented programming,

2429 computer programming easy enough for children. The idea was that manipulating

2434 Testing of Object-Oriented Programming (TOOP) FAQ

2443 Programming that have been mentioned to me over the net, in email,

2459 I am NOT a researcher on the testing of object-oriented programming.

2560 Conference on Object Oriented Programming Systems, Languages

2567 Programming", Journal of Object-Oriented Programming,

2571 object-oriented programming", Journal of Object-Oriented

2572 Programming, June, 1991, Vol. 4, No. 3, pp. 10 - 27.

2583 Smith, M. D. and D. J. Robson, "Object-Oriented Programming - the

2687 *Integration with leading programming tools for maximum productivity gains

inheritance

24 Object inheritance (or delegation)

39 Inheritance (object-oriented programming)

49 Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original form. Examples: Oberon (Oberon-1 or Oberon-2) and Common Lisp.

117 Megaobjects - Composite objects (~ subsystems with inheritance)

161 Members will denote both instance variables and methods. Inheritance is

170 inheritance. This is an example of dynamic binding, which replaces a

204 dynamic multiple inheritance (or more typically simple delegation). Here, the

216 message passing mechanism (as with dynamic scoping) than inheritance, which

270 of structure (instance variables), behavior (methods), and inheritance

355 perform inheritance this way, etc.). Because inheritance can be used to

366 1.7) What Is Inheritance? (Object-Oriented Technology)

367 Inheritance provides a natural classification for kinds of objects and allows

372 Inheritance is a relationship between classes where one class is the parent

376 etc.) class of another. Inheritance provides

379 for differential programming. Inheritance can also double for assignment

381 In delegation languages, such as Self, inheritance is delegation where objects

388 inheritance can also share parents within a class lattice (CLOS and Eiffel

390 Inheritance also provides for member lookup, or internal environment. Various

395 Defining inheritance (with a thorough description or denotational semantic

396 definition, or both) can avoid confusion about which inheritance scheme is

397 being used (especially in OOD), because inheritance has many variations and

399 Inheritance can also be used for typing, where a type or class can be used to

402 inheritance should be defined instead of over what it is, since it has many

406 instantiation relationship. In classical OO, inheritance is a relationship

408 is-a-kind-of (inheritance) are merged into one [Ungar 87, Madsen 93, Sciore

420 Differential programming is the use of inheritance to reuse existing classes

423 1.8) What Is Multiple Inheritance? (Object-Oriented Technology)

424 Multiple Inheritance occurs when a class inherits from more than one parent.

434 1.9) Does Multiple Inheritance Pose Any Additional Difficulties? (Object-Oriented Technology)

436 inheritance by simply accessing the first name encountered for data members

439 distinct parents can declare a member within a multiple inheritance hierarchy,

451 1.10) What Is Dynamic Inheritance? (Object-Oriented Technology)

452 Dynamic inheritance allows objects to change and evolve over time. Since base

457 More specifically, dynamic inheritance refers to the ability to add, delete,

459 Smalltalk provide dynamic inheritance in some form or other. Single hierarchy

460 systems, such as Self, provide dynamic inheritance in the form of delegation

464 1.11) What Is Shared (Repeated) Inheritance? (Object-Oriented Technology)

465 Multiple Inheritance brings up the possibility for a class to appear as a

466 parent more than once in a class graph (repeated inheritance), and there is

474 shared must be renamed "along an inheritance path", else they are shared by

477 1.12) Why Use Inheritance? (Object-Oriented Technology)

478 Inheritance is a natural way to model the world or a domain of discourse,

480 common in the AI domain, where semantic nets use inheritance to understand

483 Inheritance also provides for code and structural reuse. In the above Computer

497 CLOS, Eiffel, etc.) based on inheritance when type and class are bound together

506 Why Don't Some People Like Inheritance? (Object-Oriented Technology)

507 Some people complain that inheritance is hierarchical (which is what most

511 oriented languages which are then associated with the term "inheritance"

513 inheritance stuctures). Some don't like the coupling of classes (as in Jade),

515 systems that provide inheritance, inheritance provides a simple and elegant way

517 Others complain multiple inheritance is too complicated because it brings up

519 systems support Multiple Inheritance by employing semantic resolution

523 should be associations and inheritance should be reserved for a single

525 use of inheritance for typical classification. Representation "roles" can be

526 supported by dynamic multiple inheritance (DMI) in many situations.

542 Object-Based Programming usually refers to objects without inheritance

545 provide inheritance and polymorphism. Ada95 and Modula-3; however, support

546 both inheritance and polymorphism and are object-oriented. [Cardelli 85, p481]

553 object-oriented = data abstractions + object types + type inheritance

557 + Inheritance

574 Hierarchy (Inheritance)

879 inheritance, and dynamic typing in 1967 (in addition to its Algol-60 subset).

883 including classes, inheritance, a high-powered graphical environment and a

913 by) or become many different forms of object. Inheritance (or delegation)

928 adding inclusion polymorphism for subtyping and inheritance.

939 subtypes and subclasses (inheritance). Strachey's parametric polymorphism is

969 On inheritance is subtype polymorphism:

970 "Subtyping on record types corresponds to the concept of inheritance

979 polymorphism is used in practice but not enforced. For inheritance, inclusion

996 from base classes, such inheritance is an example of inclusion polymorphism

1006 acceptable and no inheritance relation is required (subtype polymorphism).

1008 Owl also had such a facility but with two separate inheritance hierarchies,

1026 constrained by inheritance: ...

1141 85] for a proper placement of ML's type system). ML doesn't use inheritance

1143 parametric polymorphism, so no inheritance is required. This is "true" or

1150 inheritance for subclassing (representation).

1175 polymorphism) but are not required to do to do so by an inheritance relation

1206 See also [Cook 90], "Inheritance Is Not Subtyping", for a formal approach.

1214 Generics are orthogonal to inheritance, since types (and classes)

1243 to the delegating of responsibility and can be applied to inheritance. When a

1249 object can be added to the delegate list, giving dynamic inheritance (of a

1251 inheritance" in which fields and methods can be added and deleted from objects.

1261 provides one, where inheritance is replaced with a roughly equivalent form

1268 of indirection and inheritance hierarchies are specified on a per object

1319 and inheritance. It is also possible to provide relational operations on an

2367 arrays and multiple inheritance). Intensive research [1] in garbage

2628 Turner, C. D. and D. J. Robson, "State-Based Testing and Inheritance",

2633 Discusses the implications of inheritance for testing,

polymorphism

23 Subtype polymorphism

496 Polymorphism is often explicitly available in many OO languages (such as C++,

498 (typing based on subclassing, or subclass polymorphism), since only an object

524 hierarchy "creation" mechanism, however this loses polymorphism and loses the

543 [Cardelli 85] and hence without polymorphism, as in '83 Ada and Modula-2.

545 provide inheritance and polymorphism. Ada95 and Modula-3; however, support

546 both inheritance and polymorphism and are object-oriented. [Cardelli 85, p481]

636 also the true essence of object-oriented polymorphism, which allows objects to

668 violates subtype polymorphism, because only subclass polymorphism is based on

899 2.1) What Is Polymorphism? (Typing - Object-Oriented Technology)

900 Polymorphism is a ubiquitous concept in object-oriented programming and is

903 Polymorphism is often considered the most powerful facility of an OOPL.

905 Polymorphism 1. State or condition of being polymorphous. 2. Cryall.

912 Polymorphism is the ability of an object (or reference) to assume (be replaced

917 object-oriented polymorphism. This is a special case of parametric

918 polymorphism, which allows an object (or reference) to assume or become any

921 provided by base classes or types (subclass and subtype polymorphism,

923 "Poly" means "many" and "morph" means "form". The homograph polymorphism has

926 definitions of polymorphism, as divided into two major forms, parametric and

928 adding inclusion polymorphism for subtyping and inheritance.

930 "Parametric polymorphism is obtained when a function works uniformly on a range

932 polymorphism is obtained when a function works, or appears to work, on several

935 Parametric polymorphism is also referred to as "true" polymorphism, whereas

936 ad-hoc polymorphism isn't (apparent polymorphism).

937 2.1) What Is Polymorphism? Cardelli and Wegner's Definition [Cardelli 85]:

938 C+W refine Strachey's definition by adding "inclusion polymorphism" to model

939 subtypes and subclasses (inheritance). Strachey's parametric polymorphism is

940 divided into parametric and inclusion polymorphism, which are closely related,

942 joined as specializations of the new "Universal" polymorphism.

946 polymorphism --|

956 Parametric Polymorphism: a polymorphic function has an implicit or explicit

959 Inclusion Polymorphism: an object can be viewed as belonging to many different

962 The two forms of "Universal Polymorphism", parametric and inclusion are closely

965 Parametric polymorphism is referred to as generics. Generics can be syntactic,

969 On inheritance is subtype polymorphism:

974 Implicit parametric polymorphism can be implemented with type inferencing

976 Inclusion polymorphism is common and is found in languages such as Simula,

977 Ada95, C++, CLOS, Eiffel and etc. (subclass polymorphism). Smalltalk also

978 uses inclusion polymorphism; its used in declaring classes, and subclass

979 polymorphism is used in practice but not enforced. For inheritance, inclusion

980 polymorphism specifies an instance of a subclass can appear wherever an

981 insta nce of a superclass is required. For subtyping (subtype polymorphism),

994 Inclusion polymorphism can refer to subtyping, or having at least as much or

996 from base classes, such inheritance is an example of inclusion polymorphism

998 polymorphism with respect to assignment (and initialization, or replacement if

1002 oriented language using inclusion polymorphism with respect to replacement;

1006 acceptable and no inheritance relation is required (subtype polymorphism).

1011 [As inclusion polymorphism covers both subtype and subclass polymorphism,

1013 2.1) What Is Polymorphism? Other Definitions

1015 polymorphism A concept in type theory, according to which a name (such as a

1019 Booch also has several sections devoted to polymorphism.

1021 conventional, classical OO and subclass polymorphism.]

1022 > Meyer's Definition [Meyer 88, sect. 10.1.5 Polymorphism]:

1023 "Polymorphism" means the ability to take several forms. In object-oriented

1031 polymorphism definition above, but here neglects the "becomes" facility

1039 functions - is sometimes called "polymorphism".

1040 [The Author notes this is a functional view of polymorphism (as provided in

1041 C++). [Stroustrup 91, p. 136] has an example of polymorphism with void *'s,

1045 "Polymorphism" means that the same operation may behave differently on

1047 2.2) What Does Polymorphism Boil Down To In OO Programming Languages? (Typing - Object-Oriented Technology)

1048 In C++, virtual functions provide polymorphism. This is because a polymorphic

1050 any object of a derived class. Is this polymorphism in itself? Objects

1058 for the polymorphic object; and hence, polymorphism. This common pure

1059 statically typed example is, of course, an example of inclusion polymorphism,

1060 subclass polymorphism to be more specific (see section 2.1). Pure statically

1061 typed subtype polymorphism, as provided in Emerald, can be implemented

1107 class inherits from. With static typing and inclusion polymorphism based on

1119 statically-typed OO languages provide polymorphism. Some approaches provide

1142 for polymorphism; unlike OO languages, but provides the prototypical example of

1143 parametric polymorphism, so no inheritance is required. This is "true" or

1144 "pure" statically (or strongly) checked parametric polymorphism, by Strachey's

1148 parametric polymorphism without static constraints (by Strachey's definition).

1149 However, Smalltalk's style uses inclusion polymorphism in practise and

1153 Subtype Polymorphism, as opposed to Subclass Polymorphism, is the best answer

1154 in OO. Parametric polymorphism is a related concept where this is also true,

1167 (transitively) from any polymorphic object's class (inclusion polymorphism

1168 based on class, or subclass polymorphism). This insures all operations to be

1175 polymorphism) but are not required to do to do so by an inheritance relation

1176 (subclass polymorphism), as is typical in most OOPLs. Dropping this

1179 this issue in Emerald. The same issue arises in parametric polymorphism

1192 similar to subtype polymorphism; however, ACs require type compatible classes

1193 to inherit from them, providing a subclass polymorphism facility, and ACs can

1202 [Jones 92] are all examples of OO systems providing subtype polymorphism.

1204 pure parametric polymorphism (as is also commonly found in OO languages in

1205 addition to inclusion polymorphism).

1208 Short Answer: Parametric Polymorphism (although various implementations

1263 variables - with subtype polymorphism making up the difference.

2366 objects, lack of polymorphism, and problems with interior pointers (e.g.

languages

44 See also: List of object-oriented programming languages

47 Languages designed mainly for OO programming, but with some procedural elements. Examples: C++, C#, VB.NET, Java, Python.

48 Languages that are historically procedural languages, but have been extended with some OO features. Examples: Visual Basic (derived from BASIC), Fortran 2003, Perl, COBOL 2002, PHP, ABAP.

49 Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original form. Examples: Oberon (Oberon-1 or Oberon-2) and Common Lisp.

50 Languages with abstract data type support, but not all features of object-orientation, sometimes called object-based languages. Examples: Modula-2 (with excellent encapsulation and information hiding), Pliant, CLU.

51 OOP in dynamic languages

67 Steve Yegge and others noted that natural languages lack the OOP approach of strictly prioritizing things (objects

86 object are interchangeable". This is a "classical languages" definition, as

89 delegation languages.

141 languages such as C++, although the new RTTI facility will supply simple

148 in more conventional languages to fully emulate this style of dynamically typed

165 A virtual member in statically typed languages is a base class member that can

175 Virtual members in dynamically typed languages are more flexible because

188 prototyping languages [Kim 89, ch3; Ungar 87, Sciore 89] have a more

190 languages. Since there is no separate class construct in these languages, and

193 classical object-oriented languages associate method, field and parent

208 languages providing high quality support for rapid prototyping, although this

235 Some languages permit arbitrary access to objects and allow methods to be

242 However most object-oriented languages provide a well defined interface to

381 In delegation languages, such as Self, inheritance is delegation where objects

384 Inherited parents can specify various flavors of state. Delegation languages

387 (Ada95, Modula-3, Object Pascal, etc.) OO languages do, but with multiple-

496 Polymorphism is often explicitly available in many OO languages (such as C++,

508 object-oriented languages provide). They would also like to see more

511 oriented languages which are then associated with the term "inheritance"

512 (although they don't need to be. For example, delegation languages allow graph

539 not have to be declared. Eiffel and BETA are examples of languages allowing

544 These languages support abstract data types (Adts) and not classes, which

564 languages and perhaps object id's for unique objects. Object id's support the

645 used in languages with static typing for simplicity and efficiency

667 requirement 1 for OO languages and Section 1.2 on Encapsulation) and also

670 Polymorphic languages can be statically typed to provide strong type checking,

788 languages

823 selection from among various languages for implementation (choosing the best

950 Polymorphic Languages: some values and variables may have more than one type.

971 (subclass) in languages, especially if records are allowed to have functional

976 Inclusion polymorphism is common and is found in languages such as Simula,

1032 as found in several dynamically typed OO languages such as Actors, CLOS,

1047 2.2) What Does Polymorphism Boil Down To In OO Programming Languages? (Typing - Object-Oriented Technology)

1053 dynamically typed languages, polymorphic objects are passed messages and will

1065 binding is found in languages such as C++ (virtual functions) and Eiffel

1111 oriented languages, since a member is defined as above in CLOS, but a member of

1119 statically-typed OO languages provide polymorphism. Some approaches provide

1128 Many languages provide dynamic typing: Smalltalk, Self, Objective-C, and etc.

1133 See section 3.4 for a categorization of common OO languages by type system.

1134 2.6) What Is This I Hear About ML And Functional Programming Languages? (Typing - Object-Oriented Technology)

1142 for polymorphism; unlike OO languages, but provides the prototypical example of

1161 In many languages, a type has a single representation insuring all operations

1164 OO languages, subclassing and dynamic binding provides for greater flexibility

1165 by providing object specialization. However, in many OO languages classes are

1203 Functional languages such as ML, Russell, and Haskell provide a separation with

1204 pure parametric polymorphism (as is also commonly found in OO languages in

1212 polymorphic functions as found in languages such as Ada, C++, Eiffel, and

1216 programming languages. An example is a Stack with a generically

1233 languages. One such popular functional language is ML, in which all functions

1250 sort). Typically, delegation and prototyping languages also have "part

1254 delegation languages usually refers to objects serving as prototypes for

1271 3.4) What Are The Major Object-Oriented Programming Languages Today?

1288 Actors Languages

1513 object-oriented languages, systems, databases and application

1553 2) OO Languages;

1670 generate OMG compliant code for OMG-specified languages).

1831 interoperability is planned so objects written in different languages can be

2088 Languages used for IDL mapping - IDL bindings for C, (or

2284 OO Languages which require garbage collection include Eiffel, Smalltalk and

2383 object. While this is often possible in procedural languages, the object-

2413 mature technology.[1] Many object-oriented languages specify garbage

2560 Conference on Object Oriented Programming Systems, Languages

systems

66 However, Niklaus Wirth (who popularized the adage now known as Wirth's law: "Software is getting slower more rapidly than hardware becomes faster") said of OOP in his paper, "Good Ideas through the Looking Glass", "This paradigm closely reflects the structure of systems 'in the real world', and it is therefore well suited to model complex systems with complex behaviours" (contrast KISS principle).

137 oriented databases and operating systems (object id's). A "proxy" based

191 only objects, they are referred to as single-hierarchy, or 1 Level systems.

202 thus performing the classical role of a class. In typical prototyping systems,

211 It is common in such systems for an object to "become" another kind of object

225 1 level systems therefore provide the most flexible and powerful capabilities.

311 describe themselves. Also called "single-hierarchy" systems.

362 "Reflective" systems are systems with MOPs (not to be confused with reflexive

363 systems, which often refer to systems implemented in terms of themselves, or

364 bootstrapped). Reflective systems are inevitably reflexive (as are most

369 and constructing object systems. Natural means we use concepts,

407 between classes only. In one-level systems, is-a (object instantiation) and

448 several classes. In classical systems without MI, a class which should inherit

460 systems, such as Self, provide dynamic inheritance in the form of delegation

509 operations available (set operations are quite common in specialized systems).

515 systems that provide inheritance, inheritance provides a simple and elegant way

519 systems support Multiple Inheritance by employing semantic resolution

582 are objects in 3 Level Systems and above because classes are instances of

585 meta-class). In 1 Level (single-hierarchy) systems, all classes are objects.

589 hybrid systems). However, all objects may be classes in single hierarchy

590 systems, since any object may act as a class (provide object instantiation or

726 operations, objects, and structures that commonly occur in software systems

728 "Systems analysis states what is done for a specific problem in a domain

730 domain. ...A domain analysis is only useful in many similar systems are to

732 cost of all the systems.

736 relevant information in a domain based on the study of existing systems and

740 localized around objects, e.g., classes, instances, systems of interacting

873 efforts places information systems within an organizational perspective by

898 systems with more resilient system organization.

1202 [Jones 92] are all examples of OO systems providing subtype polymorphism.

1245 to one of its base classes. In delegation systems, each object has a delegate

1267 delegation and classical systems, where parent classes have an extra level

1334 relational databases and see APPENDIX E, Papers, Persistent Operating Systems.

1354 3.6) What Are Object-Oriented Operating Systems?

1356 Object-Oriented Operating Systems provide resources through objects, sometimes

1358 They are almost always distributed systems (DOS or DPOS), allowing objects to

1382 See also APPENDIX E, PAPERS, Persistent Operating Systems entry.

1384 Insight ETHOS: On Object-Orientation in Operating Systems

1387 operating systems. The language used was Oberon-2. It includes

1424 See APPENDIX D for CASE systems supporting these methodologies (several from

1451 the Netherlands, and Computer Information Systems Department, Georgia

1477 Engineering of Systems, draft manuscript, 1994.

1483 Shlaer, S., Mellor, S.J. - Object-oriented systems analysis: Modeling the

1513 object-oriented languages, systems, databases and application

1514 frameworks; an abstract framework for object-oriented systems; a set

1523 communicating with OMG-conforming object-oriented systems;

1548 In order to serve OMG membership interested in other object-oriented systems

1604 integrated software systems. These systems should be built using

1607 of developers, operating systems and hardware; and enhance long-

1619 object systems. The Common Object Request Broker Architecture and

1750 distributed heterogeneous systems environments. Of all computer companies,

1764 operating systems, networking protocols or where application objects are

1799 Smalltalk. This toolset works with VisualWorks from ParcPlace Systems to

1807 3.1 or Windows NT operating systems from Microsoft(R) Corp., once

1837 and computation products and systems recognized for excellence in quality

1850 Company: Isis Distributed Systems, Inc., Ithaca NY, USA.

1881 As a fully peer-to-peer product DOME can be used to build systems

1886 suitable for use in large scale commercial systems and embedded

1887 real-time systems.

1893 integration for legacy systems.

1955 security systems providing for improved reliability of distributed systems

2044 and maintainability on systems of heterogeneous

2045 computers, operating systems and networks

2049 systems and network operating systems

2051 for implementing distributed systems:

2124 world of heterogeneous, distributed computer systems, it's an ongoing

2127 systems, applications, databases, network protocols, and the like.

2137 differences between operating systems, network protocols, databases,

2138 and file systems; access and distribute data; guarantee system

2139 security; and scale up to accommodate even the largest systems. When

2145 scale, heterogeneous, distributed systems that can run virtually any

2212 savings while freeing systems personnel to concentrate on critical

2236 operating systems, and multiple DBMSs.

2251 education. The broad technical and business systems background of our

2264 determine configuration requirements for particular computer systems.

2318 circular data structures. Two systems that use a reference count GC

2346 [4] Geodesic Systems provides GC for C and C++. See http:

2351 Geodesic Systems

2495 Software Systems", Proceedings of the 18th ACM Annual Computer

2510 Validation and Testing of Object Oriented Systems, BT Technol

2559 Object Oriented Systems, M.P.R Teltech Ltd. A poster at the

2560 Conference on Object Oriented Programming Systems, Languages

2563 Murphy, G. and P. Wong. Object-Oriented Systems Testing Methodology: An

2666 systems and so allow full portability of tests between these

software

128 * There was a Software Frameworks Assoc. and magazine until last year, but

697 etc. most programmers think of. Modern software engineering methodologies;

726 operations, objects, and structures that commonly occur in software systems

733 The key to reusable software is captured in domain analysis in that it

773 on by Grady Booch, James Rumbaugh, and Ivar Jacobson at Rational Software which

779 See [Humphrey 89] and [Yourdon 92] for a few of many discussions on software

791 software development. [Boehm 86] presents a seminal spiral life-cycle model

814 Since classes and objects are used in all phases of the OO software life-cycle,

816 gap between the phases as is often the case in other software development

831 software development and which is often required of government contractors

835 Humphrey is now working on the Personal Software Process (PSP), a scaled down

837 based software process (TSP?). Other CMM's in the works at the SEI include a

853 Kitson, D.H. and Masters, S. "An Analysis of SEI Software Process Assessment

856 Humphrey, W., Snyder, T. and Willis, R. "Software Process Improvement at

857 Hughes Aircraft", IEEE Software, July 1991

858 Dion, R., "Elements of a Process Improvement Program," IEEE Software, July

860 "Concepts on Measuring the Benefits of Software Process Improvement,"

865 software quality and ami working group in Europe helping to creat the ISO

875 processing system and software products development as integrated components.

1476 Software

1478 Jacobson, I. - Object-oriented software engineering, 1993.

1485 Wirfs-Brock, R. et.al. - Designing object-oriented software, 1990.

1504 The Object Management Group (OMG) is an international software industry

1506 (*) promotion of the object-oriented approach to software engineering

1543 application request handling software "bus."

1545 develop nor sell software of any kind. Instead, it selects and promulgates

1546 software interfaces; products which offer these interfaces continue to be

1597 commentaries from software industry leaders, informative user

1604 integrated software systems. These systems should be built using

1605 a methodology that supports modular production of software;

1609 that the object-oriented approach to software construction best

1759 the Open Software Foundation(tm) as its transport mechanism. DCE is

1892 Existing software can also be incorporated easily, providing

2100 Address -- Software Products Division-Columbia

2131 middleware - run-time system software that is layered between an

2144 Software System makes it possible for organizations to build large

2148 The DOME Software System is comprehensive middleware that provides

2218 DOME Software System Components

2219 The DOME software system is composed of the core DOME product, DOME

2255 DOME Software System and obtain quick resolutions to problems.

2327 [1] "Object-Oriented Software Construction" by Meyer puts the argument

2339 Weiser. Software --- Practise and Experience vol 18(9), pp 807-820.

2437 comp.software.testing.

2439 to the Software section. Also a couple of articles added to the

2445 Software. It is kind of like an FAQ, though it isn't organized

2448 I work for a Unix software house, Qualix Group, in the US. Here is

2479 Berard, Edward. Essays on Object-Oriented Software Engineering.

2481 This book has two chapters on testing of object-oriented software,

2484 direct from Berard Software Engineering, Ltd., 902 Wind River

2487 includes one chapter on testing OO software and one chapter

2489 Bezier, Boris, "Software Testing Techniques", 2nd edition, Van Nostrand

2492 by so many people as a definitive software testing work, that

2495 Software Systems", Proceedings of the 18th ACM Annual Computer

2503 Firesmith, D.G., "Testing Object-Oriented Software", Proceedings

2507 Northwest Conference on Software Quality, 1990, pp. 309-324.

2515 International Conference on Software Engineering, May, 1992,

2523 Hoffman, D. M. A CASE Study in Module Testing. In Proc. Conf. Software

2526 7th Australian Software Engineering Conference (to appear), 1993.

2531 at the 10th Annual Pacific Northwest Software Quality Conference,

2534 designing software that avoids acyclic component

2544 Object-Oriented Programs", IEEE Software, July 1991, pp. 72-80.

2550 Marick, Brian. The Craft of Software Testing, Prentice-Hall, in press.

2551 Makes the argument that testing of object-oriented software is

2552 simply a special case of testing software which retains state

2555 Narick, Brian. "Testing Software that Reuses", Technical Note 2, Testing

2575 Describes ways in which the usual approach to software testing

2576 could be adapted for object-oriented software.

2585 Conference on Software Maintenance 1990, IEEE Computer Society

2599 programs. Testing of OOP is compared with traditional software

2641 3.11) What Is Available On Object-Oriented Testing? Software

2660 operation. Cantata is suitable for testing software written in

2692 Software Research Inc. (625 Third St, San Francisco, CA 94107-1997,

2695 Quality Assured Software Engineering (938 Willowleaf Dr., Suite 2806,

2703 The software is available via anonymous FTP from bright.ecs.soton.ac.uk

2711 software will have the fewest problems on SunOS or Solaris releases.

data

35 coalgebraic data types

36 abstract data types (which have existential types) allow the definition of modules but these do not support dynamic dispatch

156 whose record fields are called instance variables (Smalltalk) or member data

179 member data, subclass

246 data and member functions) may be accessed from anywhere. A Stack's Push and

338 variables shared between all instances of a class (static member data in

415 Data Proc Scientific PC Workstation

436 inheritance by simply accessing the first name encountered for data members

544 These languages support abstract data types (Adts) and not classes, which

549 - It supports objects that are data abstractions with an interface of named

553 object-oriented = data abstractions + object types + type inheritance

719 including human interaction, task management, and data management details."

1662 UX, IBM RS-6000, Data General Aviion, MS-Windows (client

1693 support for heterogeneous environments, support for Remote Data Access

1945 easily integrate Orbix applications with existing data stores be they

2056 - Fine-grain Data Management - class libraries are

2125 struggle to provide easy access to data while maintaining and

2130 on-line data, information technology (IT) managers are turning to

2138 and file systems; access and distribute data; guarantee system

2146 application in the enterprise, accessing virtually any data.

2150 applications and data into a single system. With DOME, companies can

2159 - and support for Remote Data Access (RDA), Remote Procedure

2221 DOME Data Manager (DDMTM) database access manager.

2223 The DOME Data Manager is a complete relational DBMS engine that

2224 provides access to distributed data.

2226 DDM provides autonomy for distributed data sites, but it also

2227 supplies the means for consolidating data for specific applications.

2228 It can read and write data across numerous DBMSs, and it makes

2229 distributed data management transparent, so that the user never needs

2230 to know the physical location of data, the server of access, or the

2237 DDM can manipulate data across a large number of databases and data

2244 DOME, DOMEshell, DOME Security, DOME Data Manager, and DDM are

2308 arbitrary restrictions on input data which can cause failure when

2318 circular data structures. Two systems that use a reference count GC

2378 works well in simple cases like strings where the data is not polymorphic

2399 support long-lived data and keep track of ownership of data shared by

2401 c) Value semantics store objects rather than references, inhibiting data

dynamic

36 abstract data types (which have existential types) allow the definition of modules but these do not support dynamic dispatch

51 OOP in dynamic languages

135 based approaches (e.g. Smalltalk handles) allow powerful dynamic typing, as

142 dynamic typing (checked downcasting) similar to those introduced by Eiffel

147 pointer (such as void* in C++) and an embedded dynamic typing scheme are used

170 inheritance. This is an example of dynamic binding, which replaces a

195 although vtables of function pointers for dynamic binding are an exception).