Architecture, distribution and integration
Event contract — producer, schema, consumers
One topic with its schema versions, the producing service and the consumer groups — the compatibility claims drawn as a graph.
ddn@1New DDN source
Why use it?
Event breakage is a contract failure; the diagram makes "who may break whom" reviewable before a schema change ships.
When it helps
Event-driven integration: schema registry reviews, deprecation windows, consumer onboarding.
How to read it
- The producer publishes to the topic; the topic conforms to the current schema; consumers read in their own groups.
- The supersedes edge is the compatibility claim — a consumer on v2 must still read v3 events.
What you need
- The topic
- The schema versions and their compatibility
- The producer and consumer groups
Things to check
- Do not deprecate a schema version while a declared consumer still reads it.
- A consumer group with no declared purpose is an unmanaged dependency.
Scope of this diagram
Declared contract graph; wire-level schema validation against the registry is a runtime concern.
Work with the converted example
- Open the viewer and select
diagram. 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.