Earlier activity diagrams focused on actions and decisions.
The same diagram type can help you reason about where information moves during a process.
Consider a soccer application where a user enters a short lineup note.
The application may:
An activity diagram can make that movement visible.
A simple process might begin:
At this point, the information exists in the running program.
It has not necessarily been saved anywhere permanent.
If the application closes now, the information may disappear.
To preserve the note, the process needs a storage action.
Conceptually:
The important idea is that:
having information in memory is not the same as saving it to persistent storage.
The save step changes where the information exists.
A later process might be:
Now information moves from persistent storage back into the running program.
These two flows answer different questions.
Later C# code can implement the write action.
Another diagram might show:
Later C# code can implement the read action.
The diagram defines the process at a conceptual level.
The code supplies executable instructions.
A class diagram could describe:
An object diagram could describe:
An activity diagram can describe:
For storage, the third question is especially useful.
It lets you visualize the difference between information that exists during execution and information that has been saved for later use.