A prototype of a descriptive type system for Xcerpt

  • Authors:

  • Artur Wilk;Włodzimierz Drabent

  • Affiliations:

  • Dept. of Computer and Information Science, Linköping University, Linköping, Sweden;Dept. of Computer and Information Science, Linköping University, Linköping, Sweden

  • Venue:
  • PPSWR'06 Proceedings of the 4th international conference on Principles and Practice of Semantic Web Reasoning
  • Year:
  • 2006

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Abstract

The paper presents a prototype implementation of a descriptive type system for the XML query language Xcerpt. Its intended application is finding (a certain kind of) errors in programs. The implementation is able to check correctness of an Xcerpt program with respect to a type specification. A type specification describes a set of possible data bases to which the program is to be applied and an expected set of results. Program correctness means that all its results are in the expected set. Failure of a correctness check suggests an error in the program. Under certain conditions such failure indeed means that the program is incorrect. Current implementation works for a restricted, but interesting subset of Xcerpt. The system provides (approximations of) the set of program results and the sets of values of program variables; this information is useful for programmers (and is produced even when the specification of the expected set of results is not given).