Efficient Management of Multiversion Documents by Object Referencing

Traditional approaches to versioning documents are edit-based, and represent successive versions using edit scripts. This paper proposes a reference-based version-ing scheme that preserves the rich logical structure of the evolving document via object references. This approach produces better support for queries, and reconciles the storage-level and transport-level representations of multiversioned XML documents. In particular , we present eecient algorithms for supporting projection and selection queries, and for querying the document evolution history. Then, we show that our representation is also eecient at the transport level, where XML documents are exchanged between remote parties. In fact, with the reference-based scheme, an XML document's history can also be viewed and processed as yet another XML document. Finally, we demonstrate the eeectiveness of the new scheme at the storage level, for which we deene a usefulness-based page management policy, adapted from transaction-time databases, to ensure eecient temporal clustering between versions. The experimental evaluation of the new scheme against previous representations used in temporal databases and persistent-object managers shows the performance advantages of the new approach.