A Data Model and an XQuery Extension for Concurrent XML Structures

An XML document is mainly hierarhical, but some applications need to simultaneously associate more than one hierarchy to the same data. In general, concurrent hierarchies cannot be merged in order to get a well-formed XML document. This work stands in this context: it aims at describing and querying hierarchical XML structures defined over the same textual data in a concurrent way. Our proposal called MSXD is composed of a data model (which can be seen as an index over the data and between all the structures) and a dedicated query language defined as an extension of XQuery. The key idea is to propose a method for a compact description of multiple tree-like structures over a single text based on segmentation. Segmentation encoding allows querying overlap/containment relations of markups belonging to different structures. This paper also tackles a solution to define a multistructured schema in order to describe the relationships (as weak constraints) between parts of concurrent structures. Finally, this paper focuses on the architecture of the XML environment implementing our proposals.