EditorialDiagramSoftware Engineering
Editorial ER Diagram Designer — No Shadows, No Mermaid Slop
Explain the commerce domain using eight conceptual entities and explicit relationship cardinalities. Keep Customer, Order, Line item and Product meanings separate from implementation-level SQL constraints.
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Layout Grammar & Anti-Patterns
Four rules for this diagram
- 01
Use a two-section entity box: a named ENTITY header above the field list. Prefix primary identities with # and foreign references with an arrow when shown.
- 02
Connect entity boundaries and print cardinality at both relationship ends using one consistent notation: 1, N, 0..1 or 1..*.
- 03
Cluster related entities so most relationships stay straight. Use orthogonal corridors for off-axis relationships and keep cardinality labels clear of boxes.
- 04
Focus accent on the aggregate root. Field lists may have natural heights; avoid filling empty rows merely to make all boxes equal.
Three mistakes to avoid
- Treating conceptual ER relationships as SQL foreign-key delete behavior confuses domain rules with storage constraints.
- Mixing crow’s-foot marks with incompatible textual counts makes relationship ends ambiguous.
- Drawing every foreign key from a large model creates a tangle instead of a useful domain view.
Engineer vs. Executive
The two renders use the same illustrative source. Executive mode groups detail deliberately; read the captions before using an overview for a technical review.
Eight conceptual entities preserve the commerce relationships and their source cardinalities.
Five aggregate-level concepts summarize line items, addresses and product categorization.
When to use another diagram instead
Database Schema Diagram
Use physical schema for SQL types, constraints and column-to-column foreign keys.
System Architecture Diagram
Use architecture to show which services own or access the data stores.
Flowchart
Use a flowchart to explain order state decisions rather than relationships among domain entities.
Questions about this diagram
How is an ER diagram different from the database schema example?
This ER example connects conceptual entity boxes and shows cardinality, such as one Order containing one or more Line items. The physical schema example instead prints SQL types and anchors each FK to a specific column row with its deletion action. Choose according to the review question.
What does 0..1 mean on the Payment or Shipment relationship?
It means an Order may have no related entity or one related entity in this illustrative domain. It is a modeling assumption, not proof of a database uniqueness constraint. If partial payments or multiple shipments are allowed in your domain, change the source cardinality before generating a new view.
Why are Line item, Address and Category absent from Executive mode?
The five-entity overview keeps Customer, Order, Products, Payment and Shipment as aggregate-level concepts. Line-item detail, saved addresses and categorization are intentionally summarized. Engineer mode retains all eight source entities for domain-model review.
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