StateMachine vs Activity

Question

I am a little confused by the difference between the state diagram of the machine and the activity diagram in this particular situation. In the following simple diagram, can you distinguish between activity diagrams or state diagrams? Symbols are present in both charts.

thanks

Mauro

Answer 1

Now I can confirm that you cannot say. On page 331 of the UML 2.5 specification you will find an example of a receive event used in SM. The same character is used on page 409 for AD.

So the answer is: no, you cannot tell which type of chart is used from the above example.

And more generally (from the Appendix on page 683):

NOTE. This taxonomy provides a logical organization for the various main types of diagrams. However, this does not prevent mixing different types of diagrams, as can be done by combining structural and behavioral elements (for example, showing the state machine embedded in the internal structure). Consequently, the boundaries between the various types of diagrams are not strictly observed.

Answer 2

No, sometimes (for example, in this example) you cannot determine based solely on figures. but

• Usually you know which diagram is not the problem.
• names will be different. States will have nouns, while actions / actions by type of behavior are called verbs
• especially on SM, there are usually other elements that make it distinguishable: triggering events, action inside states (entry / do / exit), actions performed on transitions, SM-specific elements, such as history
• as long as receive / send signals are enabled in SM, they are hardly ever used