- •1 Scope
- •1.1 General
- •2 Conformance
- •2.1 General
- •2.2 Process Modeling Conformance
- •2.2.1 BPMN Process Types
- •2.2.2 BPMN Process Elements
- •Descriptive Conformance Sub-Class
- •Analytic Conformance Sub-Class
- •Common Executable Conformance Sub-Class
- •2.2.3 Visual Appearance
- •2.2.4 Structural Conformance
- •2.2.5 Process Semantics
- •2.2.6 Attributes and Model Associations
- •2.2.7 Extended and Optional Elements
- •2.2.8 Visual Interchange
- •2.3 Process Execution Conformance
- •2.3.1 Execution Semantics
- •2.3.2 Import of Process Diagrams
- •2.4 BPEL Process Execution Conformance
- •2.5 Choreography Modeling Conformance
- •2.5.1 BPMN Choreography Types
- •2.5.2 BPMN Choreography Elements
- •2.5.3 Visual Appearance
- •2.5.4 Choreography Semantics
- •2.5.5 Visual Interchange
- •2.6 Summary of BPMN Conformance Types
- •3 Normative References
- •3.1 General
- •3.2 Normative
- •3.3 Non-Normative
- •Activity Service
- •BPEL4People
- •Business Process Definition Metamodel
- •Business Process Modeling
- •Business Transaction Protocol
- •Dublin Core Meta Data
- •ebXML BPSS
- •Open Nested Transactions
- •SOAP 1.2
- •UDDI
- •WfMC Glossary
- •Web Services Transaction
- •Workflow Patterns
- •WSBPEL
- •WS-Coordination
- •WSDL
- •WS-HumanTask
- •XML 1.0 (Second Edition)
- •XML-Namespaces
- •XML-Schema
- •XPath
- •XPDL
- •4 Terms and Definitions
- •5 Symbols
- •6 Additional Information
- •6.1 Conventions
- •6.1.1 Typographical and Linguistic Conventions and Style
- •6.1.2 Abbreviations
- •6.2 Structure of this Document
- •6.3 Acknowledgments
- •Submitting Organizations
- •Supporting Organizations
- •Special Acknowledgments
- •7 Overview
- •7.1 General
- •7.2 BPMN Scope
- •7.2.1 Uses of BPMN
- •Private (Internal) Business Processes
- •Public Processes
- •Collaborations
- •Choreographies
- •Conversations
- •Diagram Point of View
- •Understanding the Behavior of Diagrams
- •7.3 BPMN Elements
- •7.3.1 Basic BPMN Modeling Elements
- •7.3.2 Extended BPMN Modeling Elements
- •7.4 BPMN Diagram Types
- •7.5 Use of Text, Color, Size, and Lines in a Diagram
- •7.6 Flow Object Connection Rules
- •7.6.1 Sequence Flow Connections Rules
- •7.6.2 Message Flow Connection Rules
- •7.7 BPMN Extensibility
- •7.8 BPMN Example
- •8 BPMN Core Structure
- •8.1 General
- •8.2 Infrastructure
- •8.2.1 Definitions
- •8.2.2 Import
- •8.2.3 Infrastructure Package XML Schemas
- •8.3 Foundation
- •8.3.1 Base Element
- •8.3.2 Documentation
- •8.3.3 Extensibility
- •Extension
- •ExtensionDefinition
- •ExtensionAttributeDefinition
- •ExtensionAttributeValue
- •Extensibility XML Schemas
- •XML Example
- •8.3.4 External Relationships
- •8.3.5 Root Element
- •8.3.6 Foundation Package XML Schemas
- •8.4 Common Elements
- •8.4.1 Artifacts
- •Common Artifact Definitions
- •Artifact Sequence Flow Connections
- •Artifact Message Flow Connections
- •Association
- •Group
- •Category
- •Text Annotation
- •XML Schema for Artifacts
- •8.4.2 Correlation
- •CorrelationKey
- •Key-based Correlation
- •Context-based Correlation
- •XML Schema for Correlation
- •8.4.3 Error
- •8.4.4 Escalation
- •8.4.5 Events
- •8.4.6 Expressions
- •Expression
- •Formal Expression
- •8.4.7 Flow Element
- •8.4.8 Flow Elements Container
- •8.4.9 Gateways
- •8.4.10 Item Definition
- •8.4.11 Message
- •8.4.12 Resources
- •8.4.13 Sequence Flow
- •Flow Node
- •8.4.14 Common Package XML Schemas
- •8.5 Services
- •8.5.1 Interface
- •8.5.2 EndPoint
- •8.5.3 Operation
- •8.5.4 Service Package XML Schemas
- •9 Collaboration
- •9.1 General
- •9.2 Basic Collaboration Concepts
- •9.2.1 Use of BPMN Common Elements
- •9.3 Pool and Participant
- •9.3.1 Participants
- •PartnerEntity
- •PartnerRole
- •Participant Multiplicity
- •ParticipantAssociation
- •9.3.2 Lanes
- •9.4 Message Flow
- •9.4.1 Interaction Node
- •9.4.2 Message Flow Associations
- •9.5 Conversations
- •9.5.1 Conversation Node
- •9.5.2 Conversation
- •9.5.3 Sub-Conversation
- •9.5.4 Call Conversation
- •9.5.5 Global Conversation
- •9.5.6 Conversation Link
- •9.5.7 Conversation Association
- •9.5.8 Correlations
- •9.6 Process within Collaboration
- •9.7 Choreography within Collaboration
- •9.8 Collaboration Package XML Schemas
- •10 Process
- •10.1 General
- •10.2 Basic Process Concepts
- •10.2.1 Types of BPMN Processes
- •10.2.2 Use of BPMN Common Elements
- •10.3 Activities
- •Sequence Flow Connections
- •Message Flow Connections
- •10.3.1 Resource Assignment
- •Resource Role
- •Expression Assignment
- •Parameterized Resource Assignment
- •10.3.2 Performer
- •10.3.3 Tasks
- •Service Task
- •Send Task
- •Receive Task
- •User Task
- •Manual Task
- •Business Rule
- •Script Task
- •10.3.4 Human Interactions
- •Notation
- •Manual Task
- •User Task
- •Rendering of User Tasks
- •Human Performers
- •Potential Owners
- •XML Schema for Human Interactions
- •Examples
- •10.3.5 Sub-Processes
- •Embedded Sub-Process (Sub-Process)
- •Reusable Sub-Process (Call Activity)
- •Event Sub-Process
- •Transaction
- •Ad-Hoc Sub-Process
- •10.3.6 Call Activity
- •Callable Element
- •10.3.7 Global Task
- •Types of Global Task
- •10.3.8 Loop Characteristics
- •Standard Loop Characteristics
- •Multi-Instance Characteristics
- •Complex Behavior Definition
- •10.3.9 XML Schema for Activities
- •10.4 Items and Data
- •10.4.1 Data Modeling
- •Item-Aware Elements
- •Data Objects
- •DataObject
- •States
- •Data Objects representing a Collection of Data
- •Visual representations of Data Objects
- •Lifecycle and Accessibility
- •Data Stores
- •Properties
- •Lifecycle and Accessibility
- •Data Inputs and Outputs
- •Data Input
- •States
- •Data Output
- •States
- •Service Task Mapping
- •Send Task Mapping
- •Receive Task Mapping
- •User Task Mapping
- •Call Activity Mapping
- •Script Task Mapping
- •Events
- •InputSet
- •OutputSet
- •Data Associations
- •DataAssociation
- •Assignment
- •DataInputAssociation
- •DataOutputAssociation
- •Data Objects associated with a Sequence Flow
- •10.4.2 Execution Semantics for Data
- •Execution Semantics for DataAssociation
- •10.4.3 Usage of Data in XPath Expressions
- •Access to BPMN Data Objects
- •Access to BPMN Data Input and Data Output
- •Access to BPMN Properties
- •For BPMN Instance Attributes
- •10.4.4 XML Schema for Data
- •10.5 Events
- •10.5.1 Concepts
- •Data Modeling and Events
- •Common Event attributes
- •Common Catch Event attributes
- •Common Throw Event Attributes
- •Implicit Throw Event
- •10.5.2 Start Event
- •Start Event Triggers
- •Start Events for Top-level Processes
- •Start Events for Sub-Processes
- •Start Events for Event Sub-Processes
- •Attributes for Start Events
- •Sequence Flow Connections
- •Message Flow Connections
- •10.5.3 End Event
- •End Event Results
- •Sequence Flow Connections
- •Message Flow Connections
- •10.5.4 Intermediate Event
- •Intermediate Event Triggers
- •Intermediate Events in Normal Flow
- •Intermediate Events Attached to an Activity Boundary
- •Attributes for Boundary Events
- •Activity Boundary Connections
- •Sequence Flow Connections
- •Message Flow Connections
- •10.5.5 Event Definitions
- •Event Definition Metamodel
- •Cancel Event
- •Compensation Event
- •Conditional Event
- •Error Event
- •Escalation Event Definition
- •Link Event Definition
- •Message Event Definition
- •Multiple Event
- •None Event
- •Parallel Multiple Event
- •Signal Event
- •Terminate Event
- •Timer Event
- •10.5.6 Handling Events
- •Handling Start Events
- •Handling Events within normal Sequence Flow (Intermediate Events)
- •Handling Events attached to an Activity (Intermediate boundary Events and Event Sub-Processes)
- •Interrupting Event Handlers (Error, Escalation, Message, Signal, Timer, Conditional, Multiple, and Parallel Multiple)
- •Non-interrupting Event Handlers (Escalation, Message, Signal, Timer, Conditional, Multiple, and Parallel Multiple)
- •Handling End Events
- •10.5.7 Scopes
- •10.5.8 Events Package XML Schemas
- •10.6 Gateways
- •10.6.1 Sequence Flow Considerations
- •10.6.2 Exclusive Gateway
- •10.6.3 Inclusive Gateway
- •10.6.4 Parallel Gateway
- •10.6.5 Complex Gateway
- •10.6.6 Event-Based Gateway
- •10.6.7 Gateway Package XML Schemas
- •10.7 Compensation
- •10.7.1 Compensation Handler
- •10.7.2 Compensation Triggering
- •10.7.3 Relationship between Error Handling and Compensation
- •10.8 Lanes
- •10.9 Process Instances, Unmodeled Activities, and Public Processes
- •10.10 Auditing
- •10.11 Monitoring
- •10.12 Process Package XML Schemas
- •11 Choreography
- •11.1 General
- •11.2 Basic Choreography Concepts
- •11.3 Data
- •11.4 Use of BPMN Common Elements
- •11.4.1 Sequence Flow
- •11.4.2 Artifacts
- •11.5 Choreography Activities
- •11.5.1 Choreography Task
- •11.5.2 Sub-Choreography
- •The Parent Sub-Choreography (Expanded)
- •11.5.3 Call Choreography
- •11.5.4 Global Choreography Task
- •11.5.5 Looping Activities
- •11.5.6 The Sequencing of Activities
- •11.6 Events
- •11.6.1 Start Events
- •11.6.2 Intermediate Events
- •11.6.3 End Events
- •11.7 Gateways
- •11.7.1 Exclusive Gateway
- •11.7.2 Event-Based Gateway
- •11.7.3 Inclusive Gateway
- •11.7.4 Parallel Gateway
- •11.7.5 Complex Gateway
- •11.7.6 Chaining Gateways
- •11.8 Choreography within Collaboration
- •11.8.1 Participants
- •11.8.2 Swimlanes
- •Choreography Task in Combined View
- •Sub-Choreography in Combined View
- •11.9 XML Schema for Choreography
- •12 BPMN Notation and Diagrams
- •12.1 BPMN Diagram Interchange (BPMN DI)
- •12.1.1 Scope
- •12.1.2 Diagram Definition and Interchange
- •12.1.3 How to Read this Clause
- •12.2 BPMN Diagram Interchange (DI) Meta-model
- •12.2.1 Overview
- •12.2.2 Abstract Syntax
- •12.2.3 Classifier Descriptions
- •12.2.4 Complete BPMN DI XML Schema
- •12.3 Notational Depiction Library and Abstract Element Resolutions
- •12.3.1 Labels
- •12.3.2 BPMNShape
- •Markers for Activities
- •Tasks [BPMNShape]
- •Collapsed Sub-Processes [BPMNShape]
- •Expanded Sub-Processes [BPMNShape]
- •Collapsed Ad Hoc Sub-Processes [BPMNShape]
- •Expanded Ad Hoc Sub-Processes [BPMNShape]
- •Collapsed Transactions [BPMNShape]
- •Expanded Transactions [BPMNShape]
- •Collapsed Event Sub-Processes [BPMNShape]
- •Expanded Event Sub-Processes [BPMNShape]
- •Call Activities (Calling a Global Task) [BPMNShape]
- •Collapsed Call Activities (Calling a Process) [BPMNShape]
- •Expanded Call Activities (Calling a Process) [BPMNShape]
- •Data [BPMNShape]
- •Events [BPMNShape]
- •Gateways [BPMNShape]
- •Artifacts [BPMNShape]
- •Lanes [BPMNShape]
- •Pools [BPMNShape]
- •Choreography Tasks [BPMNShape]
- •Collapsed Sub-Choreographies [BPMNShape]
- •Expanded Sub-Choreographies [BPMNShape]
- •Call Choreographies (Calling a Global Choreography Task) [BPMNShape]
- •Collapsed Call Choreographies (Calling a Choreography) [BPMNShape]
- •Expanded Call Choreographies (Calling a Choreography) [BPMNShape]
- •Choreography Participant Bands [BPMNShape]
- •Conversations [BPMNShape]
- •12.3.3 BPMNEdge
- •Connecting Objects [BPMNEdge]
- •12.4 Example(s)
- •12.4.1 Depicting Content in a Sub-Process
- •Expanded Sub-Process
- •Expanded Sub-Process with Start and End Events on Border
- •Collapsed Sub-Process
- •12.4.2 Multiple Lanes and Nested Lanes
- •12.4.3 Vertical Collaboration
- •12.4.4 Conversation
- •12.4.5 Choreography
- •13 BPMN Execution Semantics
- •13.1 General
- •13.2 Process Instantiation and Termination
- •13.3 Activities
- •13.3.1 Sequence Flow Considerations
- •13.3.2 Activity
- •13.3.3 Task
- •13.3.4 Sub-Process/Call Activity
- •13.3.5 Ad-Hoc Sub-Process
- •Operational semantics
- •13.3.6 Loop Activity
- •13.3.7 Multiple Instances Activity
- •13.4 Gateways
- •13.4.1 Parallel Gateway (Fork and Join)
- •13.4.2 Exclusive Gateway (Exclusive Decision (data-based) and Exclusive Merge)
- •13.4.3 Inclusive Gateway (Inclusive Decision and Inclusive Merge)
- •13.4.4 Event-based Gateway (Exclusive Decision (event-based))
- •13.4.5 Complex Gateway (related to Complex Condition and Complex Merge)
- •13.5 Events
- •13.5.1 Start Events
- •13.5.2 Intermediate Events
- •13.5.3 Intermediate Boundary Events
- •13.5.4 Event Sub-Processes
- •Operational semantics
- •13.5.5 Compensation
- •Compensation Handler
- •Compensation Triggering
- •Relationship between Error Handling and Compensation
- •Operational Semantics
- •13.5.6 End Events
- •Process level end events
- •Sub-process level end events
- •14 Mapping BPMN Models to WS-BPEL
- •14.1 General
- •14.2 Basic BPMN-BPEL Mapping
- •14.2.1 Process
- •14.2.2 Activities
- •Common Activity Mappings
- •Task Mappings
- •Service Task
- •Receive Task
- •Send Task
- •Abstract Task
- •Service Package
- •Message
- •Interface and Operation
- •Conversations and Correlation
- •Sub-Process Mappings
- •Mapping of Event Sub-Processes
- •Activity Loop Mapping
- •Standard Loops
- •Dealing with LoopMaximum
- •Multi-Instance Activities
- •14.2.3 Events
- •Start Event Mappings
- •Message Start Events
- •Error Start Events
- •Compensation Start Events
- •Intermediate Event Mappings (Non-boundary)
- •Message Intermediate Events (Non-boundary)
- •Timer Intermediate Events (Non-boundary)
- •Compensation Intermediate Events (Non-boundary)
- •End Event Mappings
- •None End Events
- •Message End Events
- •Error End Events
- •Compensation End Events
- •Terminate End Events
- •Boundary Intermediate Events
- •Message Boundary Events
- •Error Boundary Events
- •Compensation Boundary Events
- •Multiple Boundary Events, and Boundary Events with Loops
- •14.2.4 Gateways and Sequence Flows
- •Exclusive (Data-based) Decision Pattern
- •Exclusive (Event-based) Decision Pattern
- •Inclusive Decision Pattern
- •Parallel Pattern
- •Sequence Pattern
- •Structured Loop Patterns
- •Handling Loops in Sequence Flows
- •14.2.5 Handling Data
- •Data Objects
- •Properties
- •Input and Output Sets
- •Data Associations
- •Expressions
- •Assignments
- •14.3 Extended BPMN-BPEL Mapping
- •14.3.1 End Events
- •14.3.2 Loop/Switch Combinations From a Gateway
- •14.3.3 Interleaved Loops
- •14.3.4 Infinite Loops
- •14.3.5 BPMN Elements that Span Multiple WSBPEL Sub-Elements
- •15 Exchange Formats
- •15.1 Interchanging Incomplete Models
- •15.2 Machine Readable Files
- •15.3.1 Document Structure
- •15.3.2 References within the BPMN XSD
- •15.5 XSLT Transformation between XSD and XMI
- •B.1 Scope
- •B.2 Architecture
- •B.3 Diagram Common
- •B.3.1 Overview
- •B.3.2 Abstract Syntax
- •B.3.3 Classifier Descriptions
- •B.4 Diagram Interchange
- •B.4.1 Overview
- •B.4.2 Abstract Syntax
- •B.4.3 Classifier Descriptions
11.5.3 Call Choreography
A Call Choreography identifies a point in the Process where a global Choreography or a Global Choreography Task is used. The Call Choreography acts as a place holder for the inclusion of the Choreography element it is calling. This pre-defined called Choreography element becomes a part of the definition of the parent Choreography.
A Call Choreography object shares the same shape as the Choreography Task and Sub-Choreography, which is a rectangle that has rounded corners, two or more Participant Bands, and an Activity Name Band. However, the target of what the Choreography Activity calls will determine the details of its shape.
If the Call Choreography calls a Global Choreography Task, then the shape will be the same as a Choreography Task, but the boundary of the shape MUST have a thick line (see Figure 11.24).
If the Call Choreography calls a Choreography, then there are two options:
The details of the called Choreography can be hidden and the shape will be the same as a collapsed SubChoreography, but the boundary of the shape MUST have a thick line (see Figure 11.25).
The details of the called Choreography can be shown and the shape will be the same as an expanded SubChoreography, but the boundary of the shape MUST have a thick line (see Figure 11.26).
Figure 11.24 – A Call Choreography calling a Global Choreography Task
Figure 11.25 – A Call Choreography calling a Choreography (Collapsed)
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Figure 11.26 – A Call Choreography calling a Choreography (expanded)
Figure 11.27– The Call Choreography class diagram
The Call Choreography element inherits the attributes and model associations of ChoreographyActivity (see Figure 11.27 and Table 11.1). Table 11.4 presents the additional model associations of the Call Choreography element.
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Table 11.4 – Call Choreography Model Associations
Attribute Name |
Description/Usage |
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calledChoreographyRef: |
The element to be called, which will be either a Choreography or a |
CallableElement [0..1] |
GlobalChoreographyTask. |
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participantAssociations: |
Specifies how Participants in a nested Choreography or |
ParticipantAssociation [0..*] |
GlobalChoreographyTask match up with the Participants in the |
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Choreography referenced by the Call Choreography. |
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11.5.4 Global Choreography Task
A GlobalChoreographyTask is a reusable, atomic Choreography Task definition that can be called from within any Choreography by a Call Choreography.
The GlobalChoreographyTask element inherits the attributes and model associations of Collaboration (see Table 9.1), through its relationship to Choreography. Table 11.5 presents the additional model associations of the
GlobalChoreographyTask element.
Table 11.5 – Global Choreography Task Model Associations
Attribute Name |
Description/Usage |
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initiatingParticipantRef: |
One of the Participants will be the one that initiates the Global |
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Participant |
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Choreography Task. |
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A GlobalChoreographyTask is a restricted type of Choreography, it is an “empty” Choreography. A GlobalChoreographyTask MUST NOT contain any Flow Elements.
Since a GlobalChoreographyTask does not have any Flow Elements, it does not require
MessageFlowAssocations, ParticipantAssocations, ConversationAssocations, or Artifacts. It is basically a set of Participants and Message Flows intended for reuse.
11.5.5 Looping Activities
Both Sub-Choreographies can have standard loops and multi-instances. Examples of Choreography Activities with the appropriate markers can be seen in Figure 11.12 and Figure 11.22.
11.5.6 The Sequencing of Activities
There are constraints on how Choreography Activities can be sequenced (through Sequence Flows) in a Choreography. These constraints are due to the limited visibility of the Participants, which only know of the progress of the Choreography by the Messages that occur. When a Participant sends or receives a Message, then that
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Participant knows exactly how far the Choreography has progressed. This means that the ordering of Choreography Activities need to take into account when the Participants send or receive Messages so that they Participants are NOT REQUIRED to guess about when it is their turn to send a Message.
The basic rule of Choreography Activity sequencing is this:
The Initiator of a Choreography Activity MUST have been involved (as Initiator or Receiver) in the previous
Choreography Activity.
Of course, the first Choreography Activity in a Choreography does not have this constraint.
Figure 11.28 shows a sequence of two Choreography Activities that follow this constraint. “Participant B” is the Initiator of “Choreography Task 2” after being the Receiver in “Choreography Task 1.” While there is no requirement that “Participant B” sends the Message immediately, since there can be internal work that the Participant needs to do prior to the Message. But in this situation there is no ambiguity that “Participant B” will be the Initiator of the next Choreography Task. “Participant C” does not know exactly when the Message will arrive from “Participant B,” but “Participant C” knows that one will arrive and there are not any additional requirements on the Participant until the Message arrives.
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Pa rticipant A |
Participa nt C |
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Cho reography |
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Choreo graph y |
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Task 1 |
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Task 2 |
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Pa rticipant B |
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Participa nt B |
The Initia tor of a
Chore ograp hy Task must be involved in the previous Activity
Figure 11.28 – A valid sequence of Choreography Activities
Naturally, the sequence of Choreography Activities shown in Figure 11.28, above can be expanded into a Collaboration diagram to show how the sequence can be enforced. Figure 11.29 shows the corresponding Collaboration. The diagram shows how the Activities within the individual Pools fit with the design of the
Choreography.
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Participant A
Send
Message
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M1 |
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B |
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Participant |
Receive |
Send |
Message |
Message |
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M2 |
Participant C
Receive
Message
Figure 11.29 – The corresponding Collaboration for a valid Choreography sequence
When determining a valid sequence of Choreography Tasks, it is important to consider the type of Choreography Tasks that are being used. A single Choreography Task can be used for one or two Messages. Most of the time there will be one or two Messages for a Choreography Task. Figure 11.30 shows a sequence of Choreography Tasks, the first one being a two-way interaction, where the initiator sends a Message and gets a response from the other
Participant.
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Participan t A |
P arti ci pant A |
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Cho reogra phy |
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Ch oreog raphy |
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Task 1 |
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Ta sk 2 |
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Participan t B |
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P arti ci pant C |
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Figure 11.30 – A valid sequence of Choreography Activities with a two-way Activity
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Figure 11.31 shows the corresponding Collaboration and how the two Choreography Tasks are reflected in the
Processes within the Pools. The Choreography Task that has two Messages is reflected by three Process Tasks. Usually in these cases, the initiating Participant will use a single Activity to handle both the sending and receiving of the Messages. A BPMN Service Task can be used for this purpose and these types of Tasks are often referred to as “request-response” Tasks for Choreography modelers.
Participant C Participant B Participant A
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Se nd |
Sen d |
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and R ec ei ve |
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Mes s age |
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M es s age s |
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M 1 |
M 2 |
M3 |
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R ece iv e |
S end |
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Me ss ag e |
M es sa ge |
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R e ce iv e
Mes s age
Figure 11.31 – The corresponding Collaboration for a valid Choreography sequence with a two-way Activity
Figure 11.32 shows how a sequence of Choreography Activities can be designed that would be invalid in the sense that an Initiating Participant would not know when the appropriate time would be to send a Message. In this example, “Participant A” is scheduled to send a Message to “Participant C” after “Participant B” sends a Message to “Participant C.” However, “Participant A” will not know when the Message from “Participant B” has been sent. So, there is no way to enforce the sequence that is modeled in the Choreography.
Participant A |
Participant C |
Participant C |
C horeography |
C horeography |
C horeography |
Task 1 |
Task 2 |
Task 3 |
Participant B |
Participant B |
Participant A |
The Initiator of a
C horeography Task m ust be involved in the previous Activity
Figure 11.32 – An invalid sequence of Choreography Activities
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