Chapter 3 Building Conceptual and Logical Diagrams

Logical Diagram Basics

A Logical Data Model (LDM) allows you to validate the relationships identified in your CDM. The objects are similar to those in the CDM, but primary identifiers migrate along one-to-many relationships to become foreign identifiers, and many-to-many relationships, which are not permitted in an LDM, are replaced by intermediate entities.

The following logical diagram represent the same system as that in our CDM example (see Conceptual Diagram Basics).

Primary identifiers have migrated along one-to-many relationships to become foreign identifiers, and many-to-many relationships are replaced with an intermediary entity linked with one-to-many relationships to the extremities.