Activity diagram

From Wikipedia, the free encyclopedia
Jump to: navigation, search
UML 1.x Activity diagram for a guided brainstorming process

Activity diagrams are graphical representations of workflows of stepwise activities and actions[1] with support for choice, iteration and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and organisational processes (i.e. workflows).[2][3] Activity diagrams show the overall flow of control.

Activity diagrams are constructed from a limited number of shapes, connected with arrows.[4] The most important shape types:

  • rounded rectangles represent actions;
  • diamonds represent decisions;
  • bars represent the start (split) or end (join) of concurrent activities;
  • a black circle represents the start (initial state) of the workflow;
  • an encircled black circle represents the end (final state).

Arrows run from the start towards the end and represent the order in which activities happen.

Hence they can be regarded as a form of flowchart. Typical flowchart techniques lack constructs for expressing concurrency[citation needed]. However, the join and split symbols in activity diagrams only resolve this for simple cases; the meaning of the model is not clear when they are arbitrarily combined with decisions or loops.

While in UML 1.x, activity diagrams were a specialized form of state diagrams,[5] in UML 2.x, the activity diagrams were reformalized to be based on Petri net-like semantics, increasing the scope of situations that can be modeled using activity diagrams.[6] These changes cause many UML 1.x activity diagrams to be interpreted differently in UML 2.x

See also[edit]


  1. ^ Glossary of Key Terms at Retrieved 20 July 2008.
  2. ^ UML Revision Task Force. OMG Unified Modeling Language Specification, Version 1.4 (final draft). February 2001.
  3. ^ J. Rumbaugh, I. Jacobson, and G. Booch. The Unified Modeling Language Reference Manual. Addison-Wesley, 1999.
  4. ^ OMG Unified Modeling Language Superstructure Specification, version 2.1.1. Document formal/2007-02-05, Object Management Group, February 2007.
  5. ^ Dumas, Marlon, and Arthur H.M. Ter Hofstede. "UML activity diagrams as a workflow specification language." ≪ UML≫ 2001—The Unified Modeling Language. Modeling Languages, Concepts, and Tools. Springer Berlin Heidelberg, 2001. 76-90.
  6. ^ Störrle, Harald, and J. H. Hausmann. "semantics of uml 2.0 activities." Proceedings of the IEEE Symposium on Visual Languages and Human-Centric Computing. 2004.

External links[edit]