Modeling Tools

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I've intentionally avoided writing this chapter from the perspective of using a particular tool to build the models we'll be exploring. There is no best modeling tool. What will work best for you depends on your needs. Visio is a nice modeler, particularly if you're a Microsoft Office user . You may find that CAST Software's AppViewer is a good fit for you. Or maybe Sybase's PowerDesigner is your favorite. Perhaps you like ERwin or ER/Studio; both are excellent products. Or maybe you need a modeler that runs on a variety of operating systems, so you use magna solutions' Silverun. Whatever the case, provided you've chosen a full-featured modeling tool, you should be able to work through the examples in this chapter just fine. The tool isn't nearly as important as the concepts, and most high-end data-modeling tools support the same basic core functionality set.

One tool that's not appropriate for high-end data modeling is SQL Server's Enterprise Manager. It's Database Diagram facility is a very basic tool that provides only rudimentary physical data-modeling facilities. As you'll soon see, database design does not begin with physical data modeling; it ends there. Database design begins with understanding the business requirements driving the design, then modeling the business processes necessary to address those requirements. Once the business process modeling phase is complete, entities can be derived and relationships can be established between them. And once the entity-relationship (E-R) phase is done, logical data modeling can ensue. Once you've completed these phases, then you're ready for physical modeling. Not before. If I could have you learn just one thing from reading this chapter, it would be that database design is not a physical process; it's a mental one. Business processes, entity relationships, and logical design all drive physical database design. They control what form a database ends up taking. Database designers who neglect these foundational aspects do so at their own peril, often ending up with databases that do not adequately address business needs or that are difficult to extend or maintain. Get the basics right, and the rest will begin to fall into place.

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