What data transformations will be used to generate the required information?The designer obtains the answers to those questions from a variety of sources to compile the necessary information:Developing and gathering end-user data views. The database designer and the end user(s) jointly develop a precise description of end-user data views, which in turn are used to help identify the database’s main data elements.Directly observing the current system: existing and desired output. The end user usually has an existing system in place, whether it is manual or computer-based. The designer reviews the existing system to identify the data and its characteristics. The designer examines the input forms
and files (tables) to discover the data type and volume. If the end user already has an automated system in place, the designer carefully examines the current and desired reports to describe the data required to support the reports.Interfacing with the systems design group. As noted earlier in this chapter, the database design process is part of the SDLC. In some cases, the systems analyst in charge of designing the new system will also develop the conceptual database model. (This is usually true in a decentralized environment.) In other cases, the database design is considered part of the DBA’s job. The presence of a DBA usually implies the existence of a formal data-processing department. The DBA designs the database according to the specifications created by the systems analyst.To develop an accurate data model, the designer must have a thorough understanding of the company’s data types and their extent and uses. But data does not, by itself, yield the required understanding of the total business. From a database point of view, the collection of data becomes meaningful only when business rules are defined. Remember from Chapter 2, Data Models, that a business ruleis a brief and precise description of a policy, procedure, or principle within a specific organization’s environment. Business rules, derived from a detailed description of an organization’s operations, help to create and enforce actions within that organization’s environment. When business rules arewritten properly, they define entities, attributes, relationships, connectivities, cardinalities, and constraints.To be effective, business rules must be easy to understand, and they must be widely disseminated to ensure that every person in the organization shares a common interpretation of the rules. Using simple language, business rules describe the main and distinguishing characteristics of the data as viewed by the company. Examples of business rules are as follows:A customer may make many payments on an account.Each payment on an account is credited to only one customer.
You've reached the end of your free preview.
Want to read all 49 pages?
- Spring '17