Answering Regular Path Queries Under Approximate Semantics in Lightweight Description Logics

Abstract

Classical regular path queries (RPQs) can be too restrictive for some applications and answering such queries under approximate semantics to relax the query is desirable. While for answering regular path queries over graph databases under approximate semantics algorithms are available, such algorithms are scarce for the ontology-mediated setting. In this paper we extend an approach for answering RPQs over graph databases that uses weighted transducers to approximate paths from the query in two ways. The first extension is to answering approximate conjunctive 2-way regular path queries (C2RPQs) over graph databases and the second is to answering C2RPQs over ELH and DL-LiteR ontologies. We provide results on the computational complexity of the underlying reasoning problems and devise approximate query answering algorithms.

Answering Regular Path Queries Under Approximate Semantics in Lightweight Description Logics

“…Finally, it is not hard to transform Algorithm 1 into a polynomial time algorithm (called Algorithm 1c), that uses Dijkstra's shortest path algorithm to compute the set cert T (q, K). All the details are provided in (Fernández Gil and Turhan 2020). Thus, together with the lower bounds presented in (Bienvenu, Ortiz, and Simkus 2015) for the classical semantics, we obtain the following results.…”

“…Both, DL interpretations and basic forms of graph databases can be seen as relational structures over (unary and) binary predicates (Consens and Mendelzon 1990). For the rest of the paper we consider graph databases as finite DL interpretations (see (Fernández Gil and Turhan 2020) for a formal correspondence between the two notions). The semantics of C2RPQs over graph databases adopt the closed world assumption, i.e., answers to a C2RPQ q are simply matches in the graph database I G .…”

“…Due to space restrictions, we give the full proofs of the results in the accompanying technical report (Fernández Gil and Turhan 2020).…”