BPMN Conditional Event

in BPMN on BPMN 2.0
BPMN Conditional Event

The BPMN Conditional Event article provides a detailed explanation of the conditional event BPMN element, including the definition, notation, rules, guidelines and examples.

The BPMN Conditional Event article delves deep into the intricacies and applications of the conditional event element as outlined in the BPMN 2.0 specification. The definition, notation, and rules sections offer a concise summary of the BPMN 2.0 Specification pertaining to the conditional event element. Meanwhile, the guidelines section presents a curated collection of best practices specific to the conditional event, showcasing its proper and effective utilisation in process modelling.

BPMN Definition

Conditional triggers are implicitly thrown. When they are activated they wait for a status based condition respectively to trigger the catch Event. This type of event is triggered when a condition become true. ~ BPMN Specification

BPMN Notation

The BPMN specification defines the different types of Conditional Event elements using the following description and notation:

ElementDescriptionNotation
Conditional Start EventThis type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the Event occurs, a new process instance is started.
Conditional Event Sub-Process Event (Interrupting)This type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the Event occurs, execution of the enclosing Sub-Process is cancelled and the Event Sub-Process continues execution.
Conditional Event Sub-process Event (Non-Interrupting)This type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the Event occurs, execution of the enclosing Sub-Process continues in parallel to the Event Sub-Process.
Conditional Intermediate Catch EventThis type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the Event occurs, the event allows the process to continue.
Conditional Boundary Event (Interrupting)This type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the event occurs, the associated Activity is terminated. A downstream token is then generated, which activates the next element of the Process.
Conditional Boundary Event (Non-Interrupting)This type of Event is triggered when a condition (a type of Expression) becomes true. Whenever the Event occurs, the associated Activity continues to be active. As a token is generated for the Sequence Flow from the boundary Event in parallel to the continuing execution of the Activity.

BPMN Event Types: Conditional Events

BPMN Event Types

BPMN events represent various types of occurrences that affect the flow of a process, and they can be categorized based on their position and behavior in the process.

  • Start Event: The Start Event indicates where a particular Process will start.
  • Intermediate Event: The Intermediate Event indicates where something happens (an Event) somewhere between the start and end of a Process.
  • End Event: The End Event indicates where a Process will end.
  • Catching Events: Events that catch a trigger. All Start Events and some Intermediate Events are catching Events.
  • Throwing Events: Events that throw a Result. All End Events and some Intermediate Events are throwing Events that MAY eventually be caught by another Event.
  • Boundary Event: An Intermediate Event that is attached to the boundary of an Activity.

The following table illustrates how the different types of Conditional Events are grouped as per the BPMN Event types:

Catching EventsThrowing Events
Start EventIntermediate EventEnd Event
StandardEvent Sub-Process
Interrupting		Event Sub-Process
Non-Interrupting		CatchingBoundary
Interrupting		Boundary Non-
Interrupting		ThrowingStandard
Conditional Event

BPMN Notation: Conditional Event

BPMN Diagram

The following is an example of a BPMN Conditional Event within a diagram:

BPMN Conditional Event Example of BPMN Conditional Event

BPMN Standards & Guidelines

The difference between standard and guideline is that a standard is a level of quality or attainment while a guideline is a non-specific rule or principle that provides direction to action or behaviour. A standard are high in authority and needs to be adhered to versus a guideline is low in authority and guide one in setting standards or determining a course of action.

BPMN Standards

The BPMN Standards section contains a list of rules that are applicable to the BPMN Conditional Event as per the official rules of the BPMN Specification.

  • The condition Expression for the Event MUST become false and then true before the Event can be triggered again.
  • The condition Expression of a Conditional Start Event MUST NOT refer to the data context or instance attribute of the Process (as the Process instance has not yet been created).
  • The condition Expression of a Conditional Start Event MAY refer to static Process attributes and states of entities in the environment.

BPMN Guidelines

The BPMN guidelines section contains a list of optional rules that can be used as a guide.

  • A Conditional Start Event should have a Text Annotation describing the condition that would trigger the event.

Finally

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Reference