Study Cards on node, activity, edges
- UML 1 introduced ACTIVITY DIAGRAMS as a sort of multiple-object State Machine diagram.
- As state machines are limited to modeling the states of only one object at a time, the Activity Diagram was extended to allow the modeler to show how multiple objects could work together.
- As such, the UML 1 notation was based on the state machine notation.
- It looked like a traditional flow chart diagram with regions, called SWIMLANES, each assigned to an object to be responsible for the behaviors in that swimlane.
Instead of being based on events and transitions, Activity Diagrams became based on....
- What we call Edges, we can also call Flows depending on whether we are considering their ability to connect graphically or their carrying capacity.
Though object tokens and flows look a little different and work slightly differently from their control cousins, they have similar essential effects.
What notations do we see in the diagram?
The edges between them are control flow edges, as control information flows on these edges.
These comments are attached by dashed lines to elements that need to be annotated
They can appear on any diagram.
What is an Opaque Action?
It is not expected that UML environment would be able to enforce the rules and execute.
IF-THEN or a CASE/SWITCH pattern in code when only one condition can be true.
(first Merge than Decision)
For an action to begin executing, all of the mandatory input edges must be populated.
Because of this rule, the diagram will never execute.
Borrow this Book can only start when it has both input flows available at the same time:
The one from the Initial Node (from the left) and the one from the decision diamond (from the top).
This can never happen.
Therefore, the execution would stall. It is not an illegal diagram so your tool may not complain, so be wary.
What is this rule?
All the edges could directly connect to the final node.
You should also be able to detect which decision goes with which merge
Decision: 1 goes in, multiple goes out
Merge: Multiple going in, 1 goes out
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