Standards families
SDL system and process
ITU SDL: the system as blocks and channels, and inside a process the state machine with input, task, output and decision symbols.
sdl.basic@1New DDN source
Why use it?
SDL pairs the structural channels with the behavioural states in one standard — the two views check each other.
When it helps
Telecom and reactive-system documentation where signal protocols meet state behaviour.
How to read it
- In the system view, blocks exchange signals over named channels.
- In the process variant, read top-down: start, input, task/decision, output, next state.
What you need
- The blocks and channels
- The signal sets
- The process states and transitions
Things to check
- Do not send a signal over a channel that does not carry it.
- Every decision branch needs a continuation; an unhandled input is a stuck process.
Scope of this diagram
Declared SDL with structural validation; no code generation or exhaustive simulation is claimed.
Work with the converted example
- Open the viewer and select
system. 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.