Metadata is data that expresses the context or relativity of data. Examples of metadata include data element descriptions, data type descriptions, attribute/property descriptions, range/domain descriptions and process/method descriptions. The repository environment encompasses all corporate metadata resources: database catalogs, data dictionaries and navigation services. Metadata includes name, length, valid values and description of a data element. Metadata is stored in a data dictionary and is repository. It separates the data warehouse from changes in the schema of operational systems.