4 Chapter 4. Developing the physical data model In "The BI solutions development life cycle" on page 30 we explained the concept of the BI solutions development life cycle. Recall that the first step in the life cycle is to design a physical model of the data structures needed to support the BI solution. But what is a physical model of the data? We assume that you know the answer to this question, but also realize that all readers will not. To better understand what it is, or to get an idea of what it is, requires at least a brief look at data modeling concepts. It is a complex topic whose description could take an entire book. This is simply a terse description of a few basic terms to put them into perspective. The data infrastructure for any business is built around data models. There are actually three types of data models: conceptual, logical, and physical. Here we take a very brief look at each: Conceptual data model: This is a high-level business view of the data. It identifies the data entities used in the business and their relationships to each other. This aids in the understanding and development of the logical and physical data models. Logical data model: This is where the data model actually gets defined. Here is where the data entities are identified in detail along with any existing © Copyright IBM Corp. 2006. All rights reserved. 57