ABSTRACT
A data dictionary is a collection of data about the data. Its purpose is to rigorously define each and every data element, data structure, and data transform. A data dictionary helps to improve communication between analysts and users and between technical personnel by establishing a set of consistent data definitions. Data structures, also called group or composite data items, are defined by showing the data elements and substructures that comprise them. In the data dictionary, composite items are decomposed or partitioned down to the data element level, and each data element is fully defined. In a database, an entity is a thing about which data are stored and an occurrence is a single instance of an entity composed of data elements. A transform is a process or operation that modifies data. Many data dictionary systems allow the analyst to name, define, and record data about the transforms in the data dictionary.
