Cesar Chew at 18:57, 25 November 2014

2014-11-25T18:57:51Z

New page

:Indented line
{{Cat|BPMN|40}}

* An Event is something that “happens” during the course of a Process
* These Events affect the flow of the Process and usually have a cause or an impact. The term “event” is general enough to cover many things in a Process.
* The start of an Activity, the end of an Activity, the change of state of a document, a Message that arrives, etc., all could be considered Events
* However, BPMN has restricted the use of Events to include only those types of Events that will affect the sequence or timing of Activities of a Process.

[[File:Element type dimension.png|400px]]

== Start Event ==
[[File:Element start event.png|35px]]
* Indicates where a particular Process will start
* Does not have any incoming Sequence Flows
=== Tokens ===
* Token traverses the Sequence Flows and pass through the elements in the Process
* A token is a theoretical concept that is used as an aid to define the behavior of a Process that is being performed
* The behavior of Process elements can be defined by describing how they interact with a token as it “traverses” the structure of the Process.
* A token does NOT traverse a Message Flow

=== Start Event Semantics ===
A Start Event is OPTIONAL:
** a Process level—a top-level Process
** a Sub-Process (embedded)
** Global Process (called Process)
MAY (is NOT REQUIRED to) have a Start Event.

* If a Process is complex and/or the starting conditions are not obvious, then it is RECOMMENDED that a Start Event be used.
* If a Start Event is not used, then the implicit Start Event for the Process SHALL NOT have a trigger.
* If there is an End Event, then there MUST be at least one Start Event.

=== Processes without start event ===
* All Flow Objects that do not have an incoming Sequence Flow (i.e., are not a target of a Sequence Flow) SHALL be instantiated when the Process is instantiated.

{{Collapse|Exceptions from the rule|
Exceptions to this are:
* Compensation Activity (it has the Compensation marker). Compensation Activities are not considered a part of the normal flow and MUST NOT be instantiated when the Process is instantiated.
* Catching Link Intermediate Event, which is not allowed to have incoming Sequence Flows.
* Event Sub-Process, which is not allowed to have incoming Sequence Flows and will only be instantiated when its Start Event is triggered.
}}

*If the Start Event is used, then there MUST NOT be other flow elements that do not have incoming Sequence Flow — all other Flow Objects MUST be a target of at least one Sequence Flow

[[File:Start-event-must-not.png|200px]]

* Process without Start Event

[[File:Process-without-start-event-1.png|200px]]

[[File:Process-without-start-event2.png|200px]]

* There MAY be multiple Start Events for a given Process level.
* Each Start Event is an independent Event. That is, a Process instance SHALL be generated when the Start
Event is triggered.
* When the trigger for a Start Event occurs, a new Process will be instantiated and a token will be generated for each outgoing Sequence Flow from that Event.

<signavio>942c12f4fbda4969b40edf511af85c77:980872bc391a92b1752e1a6e0e3e43ea99dcf438ade1a63fe3be54e4b3c7e_47eb94a7af2a458c15ecdac4087b83f38dee5ceb6e8b642675c9cc363c16b2_c355d371880b9f8bf2c826424da037469cb969ab1470af9cc78aa21f26cfa4</signavio>

=== Start Event Triggers ===
Start Events can be used for these types of Processes:
* Top-level Processes
* Sub-Processes (embedded)
* Global Process (called)
* Event Sub-Processes

== Intermediate Events ==
[[File:Element intermediate events.png|35px]]

* Indicates where something happens (an Event) somewhere between the start and end of a Process
* It will affect the flow of the Process, but will not start or (directly) terminate the Process.

Intermediate Events can be used to:
* Show where Messages are expected or sent within the Process,
* Show delays are expected within the Process
* Disrupt the normal flow through exception handling
* Show the extra work needed for compensation.

=== Compensation Handling ===
*Multi-Instance

[[File:Element_multiple_instances_parallel.png|100px]]

*Loop

[[File:Element_activity_looping.png|100px]]

*Ad-hoc

[[File:Figure10-35-collapsed-ad-hoc-sub-process.png|100px]]

*Compensation

[[File:Element_compensation_association.png|200px]]

=== Throw and Catch ===
When a token arrives at an Intermediate Event that is placed within the normal flow of a Process, one of two things will happen:
* For '''throw''' Event
** trigger of the Event will immediately occur (e.g., the Message will be sent)
** the token will move down the outgoing Sequence Flow
* For '''catch'''
** the token will remain at the Event until the trigger occurs (e.g., the Message is received)
** then the token will move down the outgoing Sequence Flow

=== Types of Intermediate Events ===
TODO: Create Icon for each 12 intermediate event (Compensation, Timer, Signal etc..)

== End Event ==
[[File:Element end event.png|35px]]
* End Event indicates where a Process will end
* In terms of Sequence Flows, the End Event ends the flow of the Process, and thus, will not have any outgoing Sequence Flows
* The End Event shares the same basic shape of the Start Event and Intermediate Event, a circle with an open center so that markers can be placed within the circle to indicate variations of the Event.

=== End Event and Token ===
* End Event consumes a token that had been generated from a Start Event within the same level of Process
* If parallel Sequence Flows targets the End Event, then the tokens will be consumed as they arrive
** All the tokens that were generated within the Process MUST be consumed by an End Event before the Process has been completed

* In '''exception flow''' , if the Process is a Sub-Process, it can be stopped prior to normal completion through interrupting Intermediate Events
** In this situation the tokens will be consumed by an Intermediate Event attached to the boundary of the Sub-Process.

[[File:Element exception flow.png|200px]]

=== End Event Semantics ===
* There MAY be multiple End Events within a single level of a Process.

* An End Event is OPTIONAL: a given Process level—a Process or an expanded Sub-Process—MAY (is NOT REQUIRED to) have this shape:
** If an End Event is not used, then the implicit End Event for the Process SHALL NOT have a Result.
** If there is a Start Event, then there MUST be at least one End Event.
** If the End Event is not used, then all Flow Objects that do not have any outgoing Sequence Flow (i.e., are not a source of a Sequence Flow) mark the end of a path in the Process
** However, the Process MUST NOT end until all parallel paths have completed

* For Processes without an End Event, a token entering a path-ending Flow Object will be consumed after completion of the Flow Object
* When all tokens for a given instance of the Process are consumed, then the Process will reach a state of being completed

BPMN 2.0 Events - Revision history

Cesar Chew at 18:57, 25 November 2014