Consistently updating XML documents using incremental constraint check queries

  • Authors:

  • Bintou Kane;Hong Su;Elke A. Rundensteiner

  • Affiliations:

  • Worcester Polytechnic Institute Worcester, MA;Worcester Polytechnic Institute Worcester, MA;Worcester Polytechnic Institute Worcester, MA

  • Venue:
  • Proceedings of the 4th international workshop on Web information and data management
  • Year:
  • 2002

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Abstract

When updating a valid XML document, an efficient yet light-weight mechanism is needed to determine if the up-date would invalidate the document. Towards this goal, we developed a framework called SAXE, we first analyzed the constraints expressed in XML schema specifications and establish constraint rules that must be observed for an XML document to conform to a given XML Schema. We then classify the rules as relevant for a given update case, that is, we show the minimal set of rules that must be checked to guarantee the safety for each given update primitive. Next, we illustrate that this set of incremental constraint checks can be specified using generic XQuery expressions composed of three components. These components are (1) XML schema meta-queries to retrieve any constraint knowledge potentially relevant to the given update, (2) retrieval of specific characteristics from the to-be-modified XML, and (3) lastly an analysis of information collected about the XML schema and the affected XML document to determine validity of the update. As proof of concept, we have established a library of these generic XQuery constraint checks for the type-related constraints. The key idea of SAXE is to rewrite each XQuery update into a safe XML Query by extending it with appropriate constraint check subqueries. This enhanced XML This enhanced XML update query can then safely be executed using any existing XQuery engine that supports updates - thus turning any update engine automatically into an incremental constraint-check engine. In order to verify the feasibility of our approach, we have implemented a prototype system SAXE that generates safe XQuery updates. Our experimental evaluation assesses the overhead of rewriting, as well as the relative performance of our loosely-coupled incremental constraint check approach against the more traditional first-change-document and then revalidate-it approach.