Processes, interactions and lifecycle
UML sequence diagram with combined fragments
A full UML sequence diagram: lifelines, messages, combined fragments (alt/opt/loop), gates and time constraints.
uml.sequence@2New DDN source
Why use it?
Sequence diagrams are where protocol assumptions get written down and found out.
When it helps
Specifying or reviewing message order between components.
How to read it
- Vertical position is time; fragments bracket the conditional parts.
- A guard you cannot state in words does not belong on the diagram.
What you need
- The lifelines
- The messages in order
- The fragments and their guards
Things to check
- Do not use a fragment when you mean a separate diagram.
- Do not leave a reply message unanswered without saying so.
Scope of this diagram
Notation coverage; interactions are trace descriptions, not executable models.
Work with the converted example
- Open the viewer and select
fragments. Inspect the rendered view and its source. - Open the designer. Keep the selected profile and inspect its legal palette and property controls.
- Change one displayed title or an appropriate data value. Apply the edit and check the resulting diagram.
- Run the verifier and review its diagnostics before moving complete content into review.
- Download your edited DDN source to retain the change.
The example uses the indentation-based ddn-next-1 dialect. The language guide explains reusable definitions, dotted data rows and explicit property blocks.