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    Optimization of query plans in the presence of access limitations

    Calì, Andrea and Calvanese, D. and Martinenghi, D. (2007) Optimization of query plans in the presence of access limitations. In: 1st Workshop on Emerging Research Opportunities for Web Data Management, 2007, Barcelona, Spain.

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    We consider the problem of querying data sources that have limited capabilities and can thus only be accessed by complying with certain binding patterns for their attributes. This is often the case, e.g., in the context of data on the web queryable via web forms as well as in legacy data wrapped in relational tables. In such contexts, computing the answer to a user query cannot be done as in a traditional database; instead, a query plan is needed that takes the access limitations into account. In this paper, we develop a technique for producing a (possibly recursive) Datalog program that retrieves all obtainable answers for a query with limited source capabilities. In particular, we improve with respect to a previously published algorithm for optimizing query answering for conjunctive queries. Furthermore, we extend it to the context of unions of conjunctive queries. The algorithm exploits the structure of the query together with the binding patterns present in the source schema in order to compute an optimized query plan. The optimization excludes from the query plan the sources that are not relevant for the answer thus reducing the number of accesses to the sources.


    Item Type: Conference or Workshop Item (Paper)
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
    Depositing User: Sarah Hall
    Date Deposited: 01 Feb 2021 18:22
    Last Modified: 09 Aug 2023 12:49


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