RDF Databases for Querying XML. A Model-mapping Approach

Some recent research works face the challenge to map XML documents to RDF triples. Ontologies are used to establish semantic connections among XML applications, and some mechanisms have been defined to query them with natural XML query languages like XPath and XML Query. Generally structure-mapping approaches define a simple translation between trivial XPath expressions and a target RDF query language; however some XPath constructs (those depending on node order) cannot be covered in a structure-mapping strategy. In contrast, our work takes the model-mapping approach, respectful with the node order, that allows a complete mapping of any XPath axis to a single RDQL query. The obtained XPath processor can be fed with an unlimited set of XML schemas and/or RDFS/OWL ontologies. The queries are resolved taking in consideration the structural and semantic connections descrived in the schemas and ontologies. Such behaviour, schema-awareness and semantic integration, can be useful for exploiting schema and ontology hierarchies in XPath queries.