Diagram Atlas

DataDRAFT ENTRY

Entity–relationship diagram

A logical data model that shows entities, their important fields, and how records relate through cardinality.

Use this diagram to generate

USE WHEN

Designing or explaining a relational domain model.

AVOID WHEN

The question is how data moves at runtime.

VISUAL GRAMMAR

01entities02attributes03keys04relationships05cardinality

SEMANTIC RULES

Name entities in singular form.
Show primary and foreign keys consistently.
Put cardinality at both ends.
Omit fields that do not aid the reading task.

QUESTIONS IT ANSWERS

What data exists?
How many of one relate to another?

DRAFT MACHINE CONTRACT

id: er
status: draft
family: data
reading_task: Understand entities, keys, and cardinality.
grammar:
  - entities
  - attributes
  - keys
  - relationships
  - cardinality
checks:
  - name_entities_in_singular_form
  - show_primary_and_foreign_keys_consistently
  - put_cardinality_at_both_ends
  - omit_fields_that_do_not_aid_the_reading_task

Entity–relationship diagram

Choose by the question you need to answer.