Artifact: Event

Event	The specification of an occurrence in space and time; less formally, an occurrence of something to which the system must respond.
UML representation:	Class, stereotyped «event».
Role:	Software Architect
Optionality:	Applicable to reactive (event-driven) systems or those which utilize asynchronous messaging.
More information:	Concepts: Events and Signals Concepts: Concurrency Artifact: Signal
Purpose Properties Timing Responsibility Tailoring

Input to Activities:

Capsule Design

Class Design

Output from Activities:

Identify Design Elements

Purpose

An event is used to identify and capture information about external occurrences that the system is aware of and to which it must respond. Events can also be used to model internal events, especially exceptions.

Properties

Property Name	Brief Description	UML Representation
Name	The name of the event.	attribute
Brief Description	A brief description of the role and purpose of the event.	Tagged value, of type "short text".
Event type	one of: Signal Event, Call Event, Time Event, or Change Event	enum
Relationships	The generalizations in which the event participates.	generalization relationship
Operations	The operations defined by the event.	operation
Attributes	The attributes defined by the event.	attributes

Timing

Some events, specifically those representing the external events and the significant internal events to which the system must respond, are identified early in the elaboration phase. Other events needed to communicate asynchronously within the system are identified in the latter part of the elaboration phase. All events are architecturally significant and should be completely identified by the end of the elaboration phase.

Responsibility

The software architect is responsible for all events, ensuring that events are being used appropriately.

Tailoring

Explicitly modeling events is optional. Events should be modeled if it is essential for events to be defined and handled consistently across the system. If each developer is allowed to define their own policy for handling events, the events can be handled within statechart diagrams.