1. A system, comprising: a master data server, to maintain a master database storing master data objects, the master data server using master identifiers to identify the master data objects, the master database being accessible to clients; and an integration server, in response to a request from a client to access master data identified by a client identifier, to map the client identifier to a master identifier, retrieve a master data object from the master database based on the master identifier, and map the master data object to a mapped data object based on a set of mapping rules associated with the client.