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A signal event represents the receipt of an asynchronous signal instance. A signal event may, for example, cause a state machine
to trigger a transition.
•
MessageEvent (from Communications ) on page 463
Description
A signal event represents the receipt of an asynchronous signal. A signal event may cause a response, such as a state machine
transition as specified in the classifier behavior of the classifier that specified the receiver object, if the signal referenced
by the send request is mentioned in a reception owned or inherited by the classifier that specified the receiver object.
Attributes
• signal: Signal [1] The specific signal that is associated with this event.
Associations
No additional associations
Constraints
No additional constraints
Semantics
A signal event occurs when a signal message, originally caused by a send action executed by some object, is received by another
(possibly the same) object. A signal event may result in the execution of the behavior that implements the reception matching
the received signal.
A signal event makes available any argument values carried by the received send request to all behaviors caused by this event
(such as transition actions or entry actions).
Semantic Variation Points
The means by which requests are transported to their target depend on the type of requesting action, the target, the properties
of the communication medium, and numerous other factors. In some cases, this is instantaneous and completely reliable while
in others it may involve transmission delays of variable duration, loss of requests, reordering, or duplication. (See also
the discussion on
page 439.)
Notation
Signal events are denoted by a list of names of the triggering signals, followed by an assignment specification:
<signal-event> ::= <name> [‘(‘ [<assignment-specification>] ‘)’]
<assignment-specification> ::= <attr-name> [‘,’<attr-name>]*
where:
•
<attr-name> is an implicit assignment of the corresponding parameter of the signal to an attribute (with this name) of the
context object owning the triggered behavior.
•
<assignment-specification> is optional and may be omitted even if the signal has parameters.
Changes from previous UML
This metaclass replaces SignalEvent .