View-based query processing for regular path queries with inverse

  • Authors:

  • Diego Calvanese;Moshe Y. Vardi;Giuseppe de Giacomo;Maurizio Lenzerini

  • Affiliations:

  • Dipartimento di Informatica e Sistemistica, Università di Roma "La Sapienza", Via Salaria 113, I-00198 Roma, Italy;Department of Computer Science, Rice University, P.O. Box 1892, Houston, TX;Dipartimento di Informatica e Sistemistica, Università di Roma "La Sapienza", Via Salaria 113, I-00198 Roma, Italy;Dipartimento di Informatica e Sistemistica, Università di Roma "La Sapienza", Via Salaria 113, I-00198 Roma, Italy

  • Venue:
  • PODS '00 Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
  • Year:
  • 2000

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Abstract

View-based query processing is the problem of computing the answer to a query based on a set of materialized views, rather than on the raw data in the database. The problem comes in two different forms, called query rewriting and query answering, respectively. In the first form, we are given a query and a set of view definitions, and the goal is to reformulate the query into an expression that refers only to the views. In the second form, besides the query and the view definitions, we are also given the extensions of the views and a tuple, and the goal is to check whether the knowledge on the view extensions logically implies that the tuple satisfies the query.In this paper we address the problem of view-based query processing in the context of semistructured data, in particular for the case of regular-path queries extended with the inverse operator. Several authors point out that the inverse operator is one of the fundamental extensions for making regular-path queries useful in real settings. We present a novel technique based on the use of two-way finite-state automata. Our approach demonstrates the power of this kind of automata in dealing with the inverse operator, allowing us to show that both query rewriting and query answering with the inverse operator has the same computational complexity as for the case of standard regular-path queries.