Compilation of multiple file queries in a meta-database system
Abstract: A meta-databasesystem is constructed for describing the contents of very largedatabases. The meta-database is implemented as data structures in asymbol manipulation language, separate from the underlying databasesystem. A number of programs are built around the meta-database.The most important program module is a query compiler, whichtranslates a non-procedural query language called LRL into a lowerlevel language (COBOL). LRL permits the specification of databaseretrievals without stating which files are to be used in thesearch, or how they shall be connected. This is decidedautomatically by the query compiler. A major feature of the systemis a method, the Focus method, for compiletime optimization ofthese choices. Other facilities include the definition of "views"of the database; data directory services; authority codes; andmeta-database entry and update. Design issues discussed include the decision to compile rather thaninterpret non-procedural query languages; the decision to separatethe meta-database from the underlying database system; and theproblem of achieving an architecture convertible to any underlyingdatabase system. Experience with one such conversion isreported.
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