Evolution of DL − Lite Knowledge Bases

Abstract

Abstract. We study the problem of evolution for Knowledge Bases (KBs) expressed in Description Logics (DLs) of the DL-Lite family. DL-Lite is at the basis of OWL 2 QL, one of the tractable fragments of OWL 2, the recently proposed revision of the Web Ontology Language. We propose some fundamental principles that KB evolution should respect. We review known model and formula-based approaches for evolution of propositional theories. We exhibit limitations of a number of model-based approaches: besides the fact that they are either not expressible in DL-Lite or hard to compute, they intrinsically ignore the structural properties of KBs, which leads to undesired properties of KBs resulting from such an evolution. We also examine proposals on update and revision of DL KBs that adopt the model-based approaches and discuss their drawbacks. We show that known formula-based approaches are also not appropriate for DL-Lite evolution, either due to high complexity of computation, or because the result of such an action of evolution is not expressible in DL-Lite. Building upon the insights gained, we propose two novel formula-based approaches that respect our principles and for which evolution is expressible in DL-Lite. For our approaches we also developed polynomial time algorithms to compute evolution of DL-Lite KBs.

Updating DL-Lite Ontologies Through First-Order Queries

“…Then, we show that the careful semantics, a different formula-based update semantics proposed in the literature, is not uniquely defined in the case of DL-Lite A , contradicting a result stated in [6], which makes this update semantics inappropriate in our approach due to its inherent nondeterminism.…”

“…The most promising approaches that enjoy this property are the so-called formula-based approaches [9,13,14,23], in which the update is seen as a change of the ontology axioms. Again, several forms of formula-based instance-level updates have been considered [22,6,18,19]. Interestingly, however, for the DLs in the DL-Lite family, virtually all proposals in the literature reduce to two main approaches: the one in which we simply act on the ABox assertions explicitly stated in the ontology, and another one in which we act also on the ABox assertions that are not present but logically entailed through the use of the TBox.…”

Updating RDFS ABoxes and TBoxes in SPARQL

“…That is, on the one hand, borrowing from query rewriting techniques from DL-Lite (such as, e.g., PerfectRef [4], several refinements of which have been proposed in the literature 5 ) one can reformulate such a query to return also implied answers. While the rewritten query is exponential in the worst case wrt.…”

“…Previous work on updates in the context of tractable ontologies such as RDFS [11] and DL-Lite [5] typically has treated DELETEs and INSERTs in isolation, but not both at the same time nor in combination with templates filled by WHERE clauses, as in SPARQL 1.1; that is, these approaches are not based on BGP matching but rather on a set of ABox assertions to be updated known a priori. Pairing both DELETE and INSERT, as in our case, poses new challenges, which we tried to address by introducing different semantics and taking into account both materialised and reduced stores.…”

RDFS Update: From Theory to Practice

“…Calvanese et al also study updates to ABoxes in DL-Lite ontologies. They present a classification of the existing approaches to evolution, and show that ABox evolution under what they define as bold semantics is uniquely defined [2].…”