Querying and Updating Probabilistic Information in XML

We present in this paper a new model for representing probabilistic information in a semi-structured (XML) database, based on the use of probabilistic event variables. This work is motivated by the need of keeping track of both confidence and lineage of the information stored in a semi-structured warehouse. For instance, the modules of a (Hidden Web) content warehouse may derive information concerning the semantics of discovered Web services that is by nature not certain. Our model supports both querying (tree pattern queries with join) and updating (transactions containing an arbitrary set of insertions and deletions) over probabilistic tree data. We show that the model is as expressive as the impractical possible worlds model and that it is more expressive than a simple model where probability (confidence) is stored at each node of the tree. We briefly discuss implementation issues.