Efficient Encoding of Temporal XML Documents

The management of temporal data is a crucial issue in many applications. Recently, XML has become the standard for data exchange and representation. Consequently, important efforts have been made on the development of temporal extensions for XML. This paper investigates how to generate or maintain space-efficient time-stamped documents. We formally define a notion of compactness which allows for comparing documents. Then, we present two methods. For the first one, called general method, no restriction is made on the evolution of the XML documents whereas for the second one, called update-based method, changes are assumed to be specified by updates. For both methods, the issue is to enable processing very large documents, to use existing engines and to comply to Xquery Update Facility. The two methods are compared in terms of space-efficiency. The update-based method produces time-stamped XML documents that are more satisfactory wrt space-efficiency than the general method. This goes to show that the update-based method effectively takes advantage of the updates.