Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Author: search.filters.author.Cochrane, Roberta J.Subject: search.filters.subject.data structures

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    On Maintaining Priorities in a Production Rule System
    (1991) Agrawal, Rakesh; Cochrane, Roberta J.; Lindsay, Bruce G.; ISR
    We present a priority system which is particularly suited for production rules coupled to databases. In this system, there are default priorities between all rules and overriding user-defined priorities between particular rules. Rule processing using this system is repeatable: for a given set of rules and priorities, the rules are considered for execution in the same order if the same set of transactions is executed twice on the same initial database state. The rule order adheres to the default order as closely as possible: rules are considered in the same order as the default order unless user-defined precedence constraints force an inversion.

    We present data structures an efficient algorithms for implementing such a priority system. We show how the data structures can be incrementally maintained as user- defined priorities are altered. We also discuss how the proposed scheme can be extended to build a multi-level hierarchical priority system.

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    Relational Database Support for Complex Objects Defined by Grammars
    (1991) Cochrane, Roberta J.; Mark, Leo; ISR
    Context-free grammars provide the basis for many useful tools such as parsergenerators, compiler-compilers and syntax-directed editors. This paper demonstrates the potential benefits obtained when context-free grammars are used to define complex objects in the relational model. The grammar formalism facilitates relational queries on the hierarchical structure of these objects and promotes the use of grammar-based tools as front ends to relational database systems.
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    Implementing Set-Oriented Production Rules as an Extension to Starburst
    (1991) Widom, J.; Lindsay, Bruce G.; Cochrane, Roberta J.; ISR
    This paper describes the implementation of a set-oriented database production rule language proposed in earlier papers. Our implementation uses the extensibility features of the Starburst database system, and rule execution is fully integrated into database query and transaction processing.