25. Main elements of communication diagram: definitions, description, examples.

Communication diagrams, a kind of interaction diagram, emphasize the data links between the various participants in the interaction. Instead of drawing each participant as a lifeline and showing the sequence of messages by vertical direction as the sequence diagrams does, the communication diagram allows free placement of participants, allows you to draw links to show how the participants connect, and use numbering to show the sequence of messages.

Figure 1 shows a communication diagram for the same centralized control interaction as in Figure 2. With a communication diagram, we can show how the participants are linked together.

As well as showing links that are instances of associations, we can also show transient links, which arise only the context of the interaction. In this case, the «local» link from Order to Product is a local variable; other transient links are «parameter» and «global».

Figure 1. Communication diagram for centralized control

Figure 2. Communication diagram with nested decimal numbering

26. Composite structures: definition, description, example.

Def: Composite structure diagram visualizes the internal structure of a class or collaboration. It is a kind of component diagram mainly used in modeling a

system at micro point-of-view.

Descr: We can use the composite structure diagram to show the internal details of a classifier and to describe the objects and roles that work together to perform the behavior of the containing classifier.

We can add ports to the external structure. Ports allow you to group the required and

provided interfaces into logical interactions that a component has with the outside world

 Parts In composite structure diagrams, a part is a diagram element that represents a set of one or more instances that a containing structured classifier owns. A part describes the role of an instance in a classifier. You can create parts in the structure compartment of a classifier, and in several UML diagrams such as composite structure, class, object, component, deployment, and package diagrams.

 Ports In composite structure diagrams, a port defines the interaction point between a classifier instance and its environment or between the behavior of the classifier and its internal parts.

Example:

27. Main elements of component diagram: definitions, description, examples.

Def: Component diagram shows the physical aspect of an object-oriented software system. It illustrates the architectures of the software components and

dependencies between them.

Des:

Components are connected through implemented and required interfaces.

The important point is that components represent pieces that are independently purchasable and upgradeable. As a result, dividing a system into components is as much a marketing decision as it is a technical decision, for which is an excellent guide.

Use component diagrams when you are dividing your system into components and want to show their interrelationships through interfaces or the breakdown of components into a lower-level structure.

Example: