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Structured Activity


Structured Activity elements are used in Activity diagrams. A Structured Activity is an activity node that can have subordinate nodes as an independent Activity Group. No other Activities or their side effects should interfere with this Activity's processing.

Enterprise Architect provides two forms of Structured Activity - basic and specialized. It also applies the mechanism for creating Structured Activities to creating composite Activity elements quickly and simply.

The two basic Structured Activities are:

  • Structured Activity Node - represents an ordered arrangement of executable Activity nodes (Actions, Decisions, Merges and so on) that can include branched and nested nodes; this is the base element from which the other types of Structured Activity are derived
  • Sequential Node - represents a sequential arrangement of executable Activity nodes.

The two specialized Structured Activities are used to effectively model discreet patterns within an activity graph, defined in Clauses or Partitions:

  • Conditional node - represents an arrangement of Actions and Activities where choice determines which Activities are performed
  • Loop node - represents a sequence of Actions and Activities that are - or can be - repeated on the same object.

All four kinds of Structured Activity node are created as composite elements. However, for the Loop Node and Conditional Node elements you must create the child element structure on the parent diagram within the node element itself, as for a Composite State. You cannot develop the partitioned structure of the nodes on a child diagram. For this reason, the Show Composite Diagram facility is not available for the Loop Node and Conditional Node. It is also not available on the Structured Activity Node, as this is the base element for the Loop and Conditional Nodes. You can, however, use the two basic nodes as composite elements, and display the child diagram structure on the parent Sequential node.

When you create a Structured Activity, by selecting the icon from the Activity page of the Toolbox, the following choices are offered in a context menu:

  • Loop Node
  • Conditional Node
  • Other

The first two options specifically create a Loop or Conditional Node. The Other option displays the New Structured Activity dialog, on which you can select to create any of the four nodes, or a simple Composite Activity element.

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