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13.3.25 SignalEvent


   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


   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.


   • signal: Signal [1] The specific signal that is associated with this event.


   No additional associations


   No additional constraints


   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.)


   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>]*



   <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 .