1. A system for managing a centrally managed master repository for core enterprise reference data associated with an enterprise, comprising: a centralized master repository containing the core enterprise reference data, the core enterprise reference data being associated with a plurality of data schemas, each data schema comprising one or more data models for core enterprise reference data, each data model comprising one or more fields; and a data management services framework coupled to the centralized master repository and providing services for managing the core enterprise reference data in the centralized master repository, the services framework supporting: a master data schema comprising a union of the plurality of data models and associated fields in the plurality of data schemas; and a data thesaurus comprising, for each field in the master data schema, a set of field synonyms each representing a mapping between the field in the master data schema and a corresponding field in a particular one of the plurality of data schemas; the master data schema and data thesaurus facilitating centralized management of the core enterprise reference data in the centralized master repository across a plurality of heterogeneous external operational systems that have different associated data models and are provided indirect access to the core enterprise reference data in the centralized master repository for operational use of the core enterprise reference data according to associated business workflows.