Developing High Quality Data Models

2. Entity Relationship Model Basics

Chapter Outline

2.1 Oh, It’s Boxes and Lines Again… 9

2.2 Graphical or Lexical 10

2.3 Graphical Notations: Complexity vs. Understandability vs. Capability 11

2.4 Language and Notation Elements 12

2.4.1 Nodes 12

2.4.2 Links 12

2.4.3 Rules and Constraints 13

2.5 Express-G 13

2.5.1 Notation 13

2.5.2 Attributes and Relationships 14

2.5.3 Reading Relationships and Cardinalities 15

2.5.4 Redeclared Types 16

2.5.5 Representing a Many-to-Many Relationship as an Entity Type 16

2.5.6 Subtype/Supertype Relationships 17

2.5.7 Off-Page Connectors 18

2.6 Notation for Instances and Classes 20

2.7 Layout of Data Models 21

2.7.1 Subject Areas for ...