Editing Actor (UML) (section)


[[File:Usecase-Parent-Teacher-2 actors 5 usecases.svg|400px|thumb|right|UML [[use case diagram]] with two actors (Parent-Teacher and Child) and 5 [[use case]]s.|alt=Parent-Teacher and Child - 2 actors, 5 usecases]]

An '''actor'''<ref name=OMG>{{cite book
|chapter=Actor
|title=Unified Modeling Language 2.5.1
|series=[[Object Management Group |OMG]] Document Number formal/2017-12-05
|date=December 2017
|publisher=[[Object Management Group]] Standards Development Organization (OMG SDO)
|page=647
|url=https://www.omg.org/spec/UML/2.5.1/PDF
}}
</ref>
in the [[Unified Modeling Language]] (UML) "specifies a role played by a user or any other system that interacts with the subject."<ref name=OMG/>

"An Actor models a type of role played by an entity that interacts with the subject (e.g., by exchanging signals and data),
but which is external to the subject."<ref name="OMG UML V2.1.2">{{cite web| url= http://www.omg.org/spec/UML/2.1.2/Superstructure/PDF| title= OMG Unified Modeling Language (OMG UML), Superstructure, V2.1.2, pp. 586–588| accessdate= November 7, 2010| archiveurl= https://web.archive.org/web/20100923033721/http://www.omg.org/spec/UML/2.1.2/Superstructure/PDF| archivedate= 2010-09-23| url-status= dead}}</ref>

"Actors may represent roles played by human users, external hardware, or other subjects. Actors do not necessarily represent specific physical entities but merely particular facets (i.e., “roles”) of some entities that are relevant to the specification of its associated use cases. A single physical instance may play the role of several different actors and a given actor may be played by multiple different instances."<ref name= "OMG UML V2.1.2"/>

UML 2 does not permit associations between Actors.<ref name= "OMG UML V2.1.2"/><ref>{{cite web |url=http://www.ifi.uzh.ch/rerg/fileadmin/downloads/publications/papers/IWSSD-10.pdf |title=Problems and Deficiencies of UML as a Requirements Specification, s.3.2. |accessdate=November 7, 2010| archiveurl= https://web.archive.org/web/20101017015344/http://www.ifi.uzh.ch/rerg/fileadmin/downloads/publications/papers/IWSSD-10.pdf| archivedate= 17 October 2010 | url-status= live}}</ref> The use of generalization/specialization relationship between actors is useful in modeling overlapping behaviours between actors and does not violate this constraint since a generalization relation is not a type of association.<ref name="UML Specification">{{cite web |url=http://www.omg.org/spec/|title=UML 2 Specification |accessdate=July 4, 2012}}</ref>

Actors interact with [[use case]]s.