Data Dictionary

Wolmer’s Trust High School for Girls

INFORMATION TECHNOLOGY (General Proficiency)

 

Grade 11                                                          Teacher:  Mrs. McCallum-Rodney

 

 

Introduction and Definition

 

      The data dictionary is a specialised application of the kinds of dictionaries used as reference in everyday life.

 

      The data dictionary is a reference work of data about data (that is, metadata), one that is compiled by systems analysts to guide them through analysis and design.

 

      As a document, the data dictionary collects and coordinates specific data terms, and it confirms what each term means to different people in the organization.

 

      Data flow diagrams are an excellent starting point for collecting data dictionary entries.

      Systems analysts must be aware of and catalogue different terms that refers to the same data item.  This awareness helps them:

 

      avoid duplication of effort,

      allows better communication between organizational departments sharing a database, and

      makes maintenance more straightforward.

 

      The data dictionary can also serve as a consistent standard of data elements.

 

Need for Data Dictionaries

 

      Many database management systems now come equipped with an automated data dictionary.  These dictionaries can either be elaborate or simple.  Some computerized data dictionaries automatically catalogue data items when programming is done;  others simply provide a template to prompt the person filling in the dictionary to do so in a uniform manner for every entry.

 

      Despite the existence of automated data dictionaries, understanding what composes a data dictionary, the convention used in data dictionaries, and how a data dictionary is developed are issues that remain pertinent for the systems analyst during the systems effort. 

 

      Small systems with up to 1000 entries can still be kept effectively in a manual data dictionary.

 

      Understanding the process of compiling a data dictionary can aid the system analyst in conceptualizing the system and how it works.

 

      Data Dictionary may be used to also:

 

      Validate the data flow diagram for completeness and accuracy.

      Provide a stating point for developing screens and reports.

      Determine the contents of data stored in files.

      Develop the logic for data-flow diagram processes.