Query languages for hierarchic databases

We generalize relational data bases such as to include also hierarchic structures in the form of directories of relations and directories of directories. In this framework we study computable directory transformations which generalize the computable queries introduced by A. Chandra and D. Harel. We introduce a transformation language DL and show its completeness. The language DL can serve as a basis for specification and correctness of directory transformations and also as a basis to study their complexity. The method developed can be seen also in a broader context: It allows the general manipulation of “objects” (as in Smalltalk or SETL) and adds to it a construct for parallelism (as in VAL). We also discuss the relationship of our approach to various other models of hierarchic and object-oriented database models.

Authors

• E. Dahlhaus
• J.A. Makowsky

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