Validating quicksand: Temporal schema versioning in τXSchema

  • Authors:

  • Richard T. Snodgrass;Curtis Dyreson;Faiz Currim;Sabah Currim;Shailesh Joshi

  • Affiliations:

  • Department of Computer Science, University of Arizona, 711 Gould Simpson, P.O. Box 210077, Tucson, AZ 85721-0077, USA;Department of Computer Science, Utah State University, Logan, UT 84321, USA;Management Sciences, The University of Iowa, W322, Pappajohn Business Building, IA 52242-1994, USA;College of Information, Florida State University, 101 Louis Shores Building, 142 Collegiate Loop, Tallahassee, FL 32306-2100, USA;Expedia, Inc. 3150, 139th Avenue, SEBellevue, WA 98005, USA

  • Venue:
  • Data & Knowledge Engineering
  • Year:
  • 2008

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Abstract

The W3C XML Schema recommendation defines the structure and data types for XML documents, but lacks explicit support for time-varying XML documents or for a time-varying schema. In previous work we introduced @tXSchema, which is an infrastructure and suite of tools to support the creation and validation of time-varying documents, without requiring any changes to XML Schema. In this paper we extend @tXSchema to support versioning of the schema itself. We introduce the concept of a bundle, which is an XML document that references a base (non-temporal) schema, temporal annotations describing how the document can change, and physical annotations describing where timestamps are placed. When the schema is versioned, the base schema and temporal and physical schemas can themselves be time-varying documents, each with their own (possibly versioned) schemas. We describe how the validator can be extended to validate documents in this seeming precarious situation of data that changes over time, while its schema and even its representation are also changing.