Chapter 2 Conceptual Data Model Basics

Logical model

The logical model allows you to design the database structure and perform some database denormalization actions.

In PowerDesigner, you design a logical model using a PDM with the <Logical Model> DBMS. This PDM is a physical model with standard objects, and without DBMS specific physical options and generation capabilities.

In the database design process, you use a logical model as an intermediary step between conceptual and physical design:

• Start with a CDM containing entities, attributes, relationships, domains, data items and business rules
• Generate a logical model (PDM with the <Logical Model> DBMS). Create indexes and specify FK column names and other common features
• Generate a set of PDMs, each targeted to a specific DBMS implementation

If need be, you may develop the CDM in several design steps starting from a high level model to a low level CDM.

This design process allows you to keep everything consistent in a large development effort.

For more information on the physical data model, see the PDM User's Guide .

Copyright (C) 2005. Sybase Inc. All rights reserved.