Database Reference
In-Depth Information
CHAPTER 5
It's likely that you are reading this topic either because you've been given
a project that will make you responsible for building a data model, or you
would like to have the skills necessary to get a job doing this type of work.
(Or perhaps you are reading this topic for its entertainment value, in which
case you should seriously consider seeking some sort of therapy.)
To explain the importance of bringing your customers into the design
process, we like to compare data model design to automobile engine de-
sign. Knowing how to design an automobile engine is not something that
many people take up as a passing fancy; if you learn how to design them,
it's a good bet that you plan to make a career of it. There is a great deal of
focus on the technical details: how the engine must run, what parts are
necessary, and how to optimize the performance of the engine to meet the
demands that will be placed on it. However, there is no way to know what
those demands will be without knowing the type of automobile in which
the engine will be placed. This is also true of data models; although the log-
ical model revolves around the needs of the business, the database will be
largely dependent on the application (or applications) that will load, re-
trieve, and allow users to manipulate data.
When you're gathering requirements, you must keep both of these fac-
tors in mind. When you're building a new data model, the single most im-
portant thing to know is why, and for whom, you are designing the data
model. This requires extensive research with the users of the application that
will eventually be the interface to the database, as well as a review of any ex-
isting systems (whether they are manual processes or automated processes).
It's also important to effectively document the information you've
gathered and turn it into a formal set of requirements for the data model.
In turn, you'll need to present the information to the key project stake-
holders so that everyone can agree on the purpose, scope, and key deliver-
ables before design and development begin.
In this chapter, we discuss the key steps involved in gathering require-
ments for a project, as well as the kinds of data to look for and some
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