Search Tree Patterns for Mobile and Distributed XML Processing

As in a centralized environment, XML data processing in a peer-to-peer environment relies on basic relations between two XML fragments such as containment, subset, difference and intersection. Fast calculation of such relations based only on logical expressions like XPath is known to be a major challenge. Recently XML patterns have been introduced to model and to identify handy subclasses of XPath. We introduce a model for XML data based on their DTDs, tailored to the needs of distributed data processing. In order to meet the required granularity for data processing, our model combines concepts of tree patterns and search trees to represent XML fragments. Besides the given overview and properties of our search tree pattern model, we give an introductive example of the usage of such patterns in a peer-to-peer XML caching environment. It enables a peer's cache manager to partially contribute to other peer's requests. Identifying suitable and flexible classes of our newly introduced search tree patterns, we show that our model supports fast and resource preserving logical XML data processing, and we show how such classes can be tailored to a specific application domain and how access focus changes to XML data can be adapted.