UML activity diagram

Draft

Definition

UML activity diagrams refer to [[software engineering] method modeled with UML to describe work flows, business processes and other procedures.

They are similar to Petri nets.

Architecture of activity diagrams

Simple Activity diagrams consist of:

• Initial node.
• Activity final node.
• Activities in between

“The starting point of the diagram is the initial node, and the activity final node is the ending. An activity diagram can have zero or more activity final nodes. In between activities are represented by rounded rectangles.” ([Wikipedia], retrieved 10:15, 4 June 2008 (UTC).

Elements of the design language:

Action nodes

• Represented by a rectangle with rounded corners
• Action nodes should have a label

Control Nodes

Decision and merge

• Represented by a lozange

Fork and join

• Represented by a line
• One or more activities can join
• One or more activities can fork

Initial node

• Represented by a fat black dot
• There can be only one

Final nodes

• A fat black dot inside a circle
• A circle with an x represents the end of a flow (not the whole activity)

Object nodes

• Represented by a rectangle with a label

Activity edges (links)

Control edges

These edges can be drawn in various ways:

• Represented by an arrow from an activity node to another
• Represented by an arrow from an activity showing parameters with pins from a node to another
• An arrow to a connector (a small circle with a letter) and then from a same connector to a activity node
• Activity node to object node to activity node (with arrows)

Object Flow edges

• Represented by an arrow

Subactivities

• Activities can be decomposed into subactivities
• A rake in an action node signals a subactivity
• The subsidiary activity diagram has an input and an output parameter (object nodes)

Partitions

Activity diagrams can be partioned according to roles (e.g. learner A, learner B, group A, teacher)

Signals

Actions in a diagram also can respond to signals (instead of the flow)

Time signals

• Represented like an hour glass

Accept signal

• Represented by smashed-in rectangle ;)

In education

Activity diagrams can be used to describe learning designs of CSCL scenarios. A good example are collaborative learning flow pattern (

Links

Summaries of UML activity diagrams

• Wikipedia:Unified_Modeling_Language (Wikipedia)
• Activity diagram (Wikipedia)

Introductions to activity diagrams

• UML 2 Activity Diagrams, and UML 2 Activity Diagram Guidelines by Scott W. Ambler, Ambysoft.
• UML 2 Activity and Action Models by Conrad Bock, U.S. National Institute of Standards and Technology

References

• Fowler, M. (2000). UML distilled (3rd ed.). Upper Saddle River, NJ: Addison-Wesley. ISBN 0321193687

• Hernández-Leo, D., Asensio-Pérez, J.I., Dimitriadis, Y., Bote-Lorenzo, M.L., Jorrín-Abellán, I.M., Villasclaras-Fernández, E.D. (2005b). Reusing IMS-LD Formalized Best Practices in Collaborative Learning Structuring. Advanced Technology for Learning 2(4):223-232. http://dx.doi.org/10.2316/Journal.208.2005.4.208-0865 - PDF