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A Diagram Gate used in Sequence, Timing, Communication and Interaction diagrams using Sparx Systems Enterprise Architect.


A Diagram Gate is a simple graphical way to indicate the point at which messages can be transmitted into and out of Interaction Fragments. A fragment might be required to receive or deliver a message; internally; an ordered message reflects this requirement, with a Gate indicated on the boundary of the fragment's frame. Any external messages 'synching' with this internal message must correspond appropriately. Gates can appear on Interaction diagrams (Sequence, Timing, Communication or Interaction Overview), Interaction Occurrences and Combined Fragments (to specify the expression).

An example of a Diagram Gate used in a Sequnce diagram modeled in Sparx Systems Enterprise Architect.

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Diagram Gate element

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OMG UML Specification:

The OMG Unified Modeling Language specification, (v2.5.1, pp.575-576) states:

A Gate is a MessageEnd that is used on the boundary of an Interaction, or an InteractionUse, or a CombinedFragment to establish the concrete sender and receiver for every Message.

Gate instances, since they occur in a paired manner linking two Message instances, are also not themselves explicitly ordered. Gates are MessageEnds that provide a connection point between, either:

  • a Message instance outside of an InteractionUse and a Message instance inside the used Interaction, or
  • a Message instance outside a CombinedFragment and a Message instance inside an InteractionOperand within the CombinedFragment.