Heterogeneous Database Access

This thesis presents a design for accessing commercially available data bases and other data base systems from a given, 'local" data base system. Using this design, data from the local data base and from one or more "foreign" data bases will be integrated in framing the response to a single query. The design does not presume any standardization or integration of any kind on the part of a target data base.An expert system has been designed, to be used by the applications programmer, for acquiring the information about a target data base, the communication path with the target computer, and the protocol for sending a data retrieval request. It also obtains from the applications programmer the nature of the data to be accessed and instructions for converting the incoming data into the "local" system's own format. This information is then associated with each word referring to data residing in the "foreign" data base, and is stored in the lexicon of the "local" system. The design also includes the extension of the underlying, host, system so that this information is properly used at the appropriate points in the processing of a user query