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What is a Data Dictionary?

Troy Holmes
Troy Holmes

A computer database is a digital file system that maintains critical information for a company. A data dictionary is a detailed data map of each element and file table within the database. This map is considered a data catalog that includes each table name, field name, field type, and a general description of all the elements within the database.

The data dictionary is one of the most critical documents for a computer application. It provides a general description of the contents of the data within the database. It also defines the format rules, constraints, and rules for data integrity. Without this dictionary, future modification to the application could become impossible.

Woman doing a handstand with a computer
Woman doing a handstand with a computer

Many legacy software applications have an archaic database design. This is due to the physical limitations of databases designed many decades ago. Because of the field name size constraints, many names are abbreviated and not very intuitive. A data dictionary is a necessity for managing legacy databases.

Unfortunately, there is no formal auditing process for database design. It is typically the responsibility of the development team to implement best practices when creating a database. Many novice developers may define column names with generic descriptions. This generic naming convention is extremely non-intuitive and poor practice, which can lead to an unmanageable database.

A data dictionary can assist with non-intuitive database design. This dictionary will define each field name and the metadata in detail, with a description of how the data is used. Having this dictionary can help future developers determine how to best modify the system for future enhancements.

A database is made up of tables and field names. The table is a file that contains information about a specific type of data. An example of a table could be a person table. The person table would have field names to include first name, last name, and middle name. The data dictionary is the document that defines the details about each field within the tables of database.

The data dictionary is similar to a catalog system within a library. Each table is documents as a specific unit with a detail definition of the field names within the table. The definition should include the size, type, and expected values of the fields. It should also define any relationships the table may have with other data elements within the database.

A required field is a data element that must always be populated before the application will allow data to be saved into the file system. Not all data elements are considered required fields. The data dictionary should also document which fields are required fields. This helps future development team understand the rules incorporated in the database.

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