XML Query Data Model

• based on the Post-Schema-Validation Infoset, or PSVI (the XML Infoset, augmented by any type information provided by an XML Schema)
• "ordered forests" and "unordered forests" model collections of documents
• they also model node collections, similar to XPath node-sets
• references are used to model intra-document references such as ID/IDREF relationships
• they also model inter-document references, eg. XLink
• an instance of the data model serves as input to and output from queries, thus fulfilling the requirement for closure
• http://www.w3.org/TR/query-datamodel