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XML with data values: typechecking revisited |
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| Authors: | Noga Alon |
| Affiliation: | a Computer Science Department, Tel Aviv University, Tel Aviv 69978, Israel b University of Limburg (LUC), Department WNI, Universitaire Campus, B-3590 Diepenbeek, Belgium c Computer Science and Engineering, University of Washington, Box 352350, Seattle, WA 91895-2350, USA d Department of Computer Science and Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0114, USA |
| Abstract: | We investigate the typechecking problem for XML queries: statically verifying that every answer to a query conforms to a given output DTD, for inputs satisfying a given input DTD. This problem had been studied by a subset of the authors in a simplified framework that captured the structure of XML documents but ignored data values. We revisit here the typechecking problem in the more realistic case when data values are present in documents and tested by queries. In this extended framework, typechecking quickly becomes undecidable. However, it remains decidable for large classes of queries and DTDs of practical interest. The main contribution of the present paper is to trace a fairly tight boundary of decidability for typechecking with data values. The complexity of typechecking in the decidable cases is also considered. |
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