The Data

Abstract

Chapter 8 focused on application specifications as they relate to process. Using DFDs, PFDs, state diagrams, etc., I showed how data elements are defined in the DD. However, the process of completing the DD and building complex relational databases has further steps. This chapter focuses on how to design databases for use with e-commerce Web applications. The completion of the DD and the creation of the database schematic, called the entity relational diagram, provide developers with the data architecture component of the system. We call the process of creating this architecture logic data modeling. The process of logic data modeling not only defines the architecture, but it also provides the construct for the actual database, often called the physical database. The physical database differs from its logical counterpart in that it is subject to the rules and formats of the database product that will be used to implement the system. This means that if Oracle is used to implement the logical schema, the database must conform to the specific proprietary formats that Oracle requires. Thus, the logical model provides the first step in planning for the physical implementation. First, we will examine the process of building the appropriate schematic. Even if a package software product is selected, the chances are that it will need to use a database product like Oracle. Thus, many of the analysis and design below will be extremely important in determining the best fit for a package.