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A change event models a change in the system configuration that makes a condition true.
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Event (from Communications ) on page 459
Description
A change event occurs when a Boolean-valued expression becomes true. For example, as a result of a change in the value held
in a slot corresponding to an attribute, or a change in the value referenced by a link corresponding to an association. A
change event is raised implicitly and is not the result of an explicit action.
Attributes
No additional attributes
Associations
Issue 8302 -add subsets constraint
| • | changeExpression: Expression [1] | A Boolean-valued expression that will result in a change event whenever its value changes from false to true. {Subsets Element::ownedElement} | |||
| Constraints | |||||
| No additional constraints | |||||
| Semantics |
Each time the value of the change expression changes from false to true, a change event is generated.
Semantic Variation Points
It is a semantic variation when the change expression is evaluated. For example, the change expression may be continuously
evaluated until it becomes true. It is further a semantic variation whether a change event remains until it is consumed, even
if the change expression changes to false after a change event.
Notation
A change event is denoted in a trigger by a Boolean expression.
<change-event> ::= ‘when’ <expression>
Changes from previous UML
This metaclass replaces change event.