Data structures and meaning
Chen ER notation — extended
Classic Chen entity-relationship notation: entity rectangles, relationship diamonds, attribute ovals, extended with the weak/identifying marks.
chen.binary@2New DDN source
Why use it?
Chen separates the relationship (diamond) from the entity visually — the notation that teaches what a relationship *is*.
When it helps
Teaching, conceptual modelling, or anywhere the relationship itself carries attributes.
How to read it
- Rectangles are entities, diamonds are relationships, ovals are attributes; double lines mark total participation.
- Cardinality is written as numbers on the connecting lines.
What you need
- The entities
- The relationships (with their own attributes if any)
- The cardinalities
Things to check
- Do not hang an attribute on a line — it belongs to an entity or a relationship, say which.
- A diamond with one entity is usually a missing entity.
Scope of this diagram
Declared ER structure; mapping to a relational schema is the logical-modelling step (see that chapter).
Work with the converted example
- Open the viewer and select
chen_extended. 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.