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. Actors may represent roles played by human users, external hardware, or other subjects. Note that an actor does not necessarily represent a specific physical entity but merely a particular facet (i.e., "role") of some entity that is relevant to the specification of its associated use cases. Thus, a single physical instance may play the role of several different actors and, conversely, a given actor may be played by multiple different instances.
While UML 2 does not permit associations between Actors, this constraint is often violated in practice since the generalization/specialization relationship between actors is useful in modeling overlapping behaviours between actors. The actors below are represented as having a hierarchical relationship for ease of understanding; however, these relationships can easily be removed.
- Cancer Researcher
- Clinical Researcher
- Basic Science Researcher
- Protocol Designer
- Information Technologist
- Information Modeler
- Software Engineer
- Systems Architect
- System Administrator
- Metadata Specialist
- Metadata Curator
- Metadata Systems Manager
- Patient
- Subject (study participant)
