Gate   A gate is a type of message end that represents the connection point between a message that exists within an interaction fragment and a message outside the interaction fragment. A gate is a formal mechanism for connecting messages ensuring that every message has a sender and a receiver. Gates can exist in a number of contexts: formal gates used in interactions, actual gates used in interaction occurrences and expression gates used in combined fragments.

Explanation

A gate is a point on a frame where a message ends, indicating that it is connected to another message that lies outside the scope of the frame. The purpose of a gate is to ensure that there are no dangling messages in a model. The gate is used as a reference point and refers to another message outside the frame. This effectively allows a message to be followed or traced from one diagram and picking up the trace in another context. This concept exist in our daily lives when we use a road map, at the point a road reaches the edge of the map it is labeled with a name that indicates that it is referenced in another map and usually indicates where the road will lead to if followed on the adjoining map (e.g. See map: 57 to "Rome").

Related Entries

Interaction Occurrence  Owner of Element,  Used Together A interaction occurrence is related to a gate in that an interaction occurrence can contain a gate on its frame marking the point that a message references a message outside the scope of the interaction fragment.