Query Rewriting for Horn-SHIQ Plus Rules

Abstract

Query answering over Description Logic (DL) ontologies has become a vibrant field of research. Efficient realizations often exploit database technology and rewrite a given query to an equivalent SQL or Datalog query over a database associated with the ontology. This approach has been intensively studied for conjunctive query answering in the DL-Lite and EL families, but is much less explored for more expressive DLs and queries. We present a rewriting-based algorithm for conjunctive query answering over Horn-SHIQ ontologies, possibly extended with recursive rules under limited recursion as in DL+log. This setting not only subsumes both DL-Lite and EL, but also yields an algorithm for answering (limited) recursive queries over Horn-SHIQ ontologies (an undecidable problem for full recursive queries). A prototype implementation shows its potential for applications, as experiments exhibit efficient query answering over full Horn-SHIQ ontologies and benign downscaling to DL-Lite, where it is competitive with comparable state of the art systems.

First Order Rewritability in Ontology-Mediated Querying in Horn Description Logics

“…For Horn-SHIQ KBs, we follow the definition in (Eiter et al 2012), and for Horn-DLFD the definition in (McIntyre et al 2019). For more general but expressively equivalent syntax, e.g., that allows other forms of qualified number restrictions, see (Hustadt, Motik, and Sattler 2005;St.…”

“…For details please see (Eiter et al 2012) and (Toman and Weddell 2013;St. Jacques, Toman, and Weddell 2016;McIntyre et al 2019), respectively.…”

“…Note that subsumptions of the form "A1 • • • An B" are also allowed in(Eiter et al 2012). Here, we are appealing to an obvious conservative extension to replace such subsumptions with strictly binary use of conjunction to further simplify our presentation.…”

Integration-Oriented Ontology

“…Prominent results of generic reasoning OBDA systems are Ontop (see Calvanese et al (2017)), Grind (see Hansen and Lutz (2017)) or Clipper (see Eiter et al (2012)). Ontop provides an end-to-end solution for OBDA, which is integrated with existing Semantic Web tools such as Protégé or Sesame.…”

Query Rewriting Optimisation Techniques for Ontology-Based Data Access

“…Clipper [Eiter et al, 2012] aims at more expressive logics, more precisely Horn-SHIQ. This approach can rewrite the ontology including TBox and ABox or only the TBox.…”