Section: New Results
Querying Heterogeneous Linked Data
The PhD project of Lozano on relational to RDF data integration is progressing under the direction of Boneva, and Staworko. At AMW  they studied the relational to RDF data exchange problem. They focus in particular on a preliminary analysis of the consistency problem for relational to RDF data exchange with target ShEx schema.
Shape Expression Language 2.0 (ShEx) is a language to describe the vocabulary and the structure of an RDF graph. It is base on the notion of shapes, a typing system supporting algebraic operations, recursive references to other shapes or Boolean combination.
In their PODS paper , Staworko studied the containment problem for ShEx (in cooperation with Wieczorek from Wrazlaw). Containement is a classical subject for schema-related issue in database theory. The authors proved that it is decidable for ShEx-schema, but with a untractable complexity (co-NEXP -hard). They also carefuly craft restriction of ShEx schema to design tractable-but-still-signifiant fragments.