Despite what you may have heard, the time it takes to establish field specifications for each field in the database is an investment toward building consistent data and quality informationyou are not wasting time whatsoever by performing this process. In fact, you'll waste more time in the end if you only partially perform this process or neglect it entirely. Shirking this duty means you're bound to encounter (and suffer from) inconsistent and erroneous data and inaccurate information.
There are several reasons why field specifications are crucial:
Field specifications help establish and enforce field-level integrity. Implementing these specifications enables you to guarantee that the data in each field is consistent and valid.
Defining field specifications for each field enhances overall data integrity. Remember that field-level integrity is one of the four components of overall data integrity. Field-level integrity enhances (to some extent) the table-level integrity you established in the previous stage of the design process. (This will become apparent when you work with the logical elements of the field specification.)
Defining field specifications compels you to acquire a complete understanding of the nature and purpose of the data in the database. Understanding the data means that you can judge whether the data is truly necessary and important to the organization, and you can learn how to use it to your best advantage.
Field specifications constitute the "data dictionary" of the database. Each field specification stores data on the characteristics of a particular field within the database. The complete set of specifications you establish for all of the fields in the database composes a literal dictionary of the database's structure. This data dictionary is particularly useful when you implement your database in an RDBMSyou can use it as a guide for creating the fields and setting their fundamental properties. These specifications will also help you determine what type of data-entry and data-validation procedures you need to implement within any user-interface application you create for the database.
Keep in mind that the levels of consistency, quality, and accuracy of the data in the database (and information retrieved from that data) are in direct proportion to the degree that you complete these specifications. It is paramount that you establish each field specification completely if your organization depends heavily on the information you retrieve from the database.