The current paper have been accepted at the International Joint Conference on Rules and Reasoning (RuleML+RR 2017). We focus on Query rewriting, a popular approach for ontology based data access and in general for first order rewritable knowledge bases. The algorithms defined in the field are based on conjunctive queries with no use of negation over the atoms that are part of them. Also, the co...

Querying large databases while taking ontologies into account is currently a very active domain research. In this paper, we consider ontologies described by existential rules (also known as Datalog+/-), a framework that generalizes lightweight description logics. A common approach is to rewrite a conjunctive query w.r.t an ontology into a union of conjunctive queries (UCQ) which can be directly...

In this paper, we analyze the dictionary definitions of verbs for finding units of a definition, and study the reconstruction of the dictionary definitions without ambiguity. For finding units of the definition, we analyze the dependency structures of definitions and make a relation between main verb and other syntactic units. We build a hierarchical structure by using the relation between a he...

Conjunctive match is often used in Artificial Intelligence as the kernel of a pattern-directed inference [37] engine. Conjunctive match entails generating and testing all possible combinations of objects against a pattern of constraints. While simple to program, it is an expensive, exponential cost computation. To reduce this average match cost in production system engines, the RETE match algor...

Querying large databases while taking ontologies into account is currently a very active domain research. In this paper, we consider ontologies described by existential rules (also known as Datalog+/-), a framework that generalizes lightweight description logics. A common approach is to rewrite a conjunctive query w.r.t an ontology into a union of conjunctive queries (UCQ) which can be directly...

ast that early-s evaluate 37 by examining cast. We use a eparately and of the experts' correct forecasts. We then compare predictions derived from the conjunctive model, analysts' ns. The 82.6%, out-of-time tests. Results indicate that simple decision heuristics perform better than ABSTRACT We investigate the decision heuristic used by experts to forec stage R&D projects are subsequently commer...

We study the evaluation of positive conjunctive queries with Boolean aggregate tests (similar to HAVING queries in SQL) on probabilistic databases. Our motivation is to handle aggregate queries over imprecise data resulting from information integration or information extraction. More precisely, we study conjunctive queries with predicate aggregates using MIN, MAX, COUNT, SUM, AVG or COUNT(DISTI...

Farmers in the Indus Basin, Pakistan have generally switched to groundwater for additional water supplies due to the irregular supply of irrigation water; currently over 50% of the agricultural land in the basin is at least partially irrigated by tubewells. These wells pump fresh groundwater, which essentially is the result of massive leakage from irrigation canals into the originally saltwater...

We study conjunctive query answering and first-order rewritability of conjunctive queries for binary guarded existential rules. In particular, we prove that the problem of establishing whether a given set of binary guarded existential rules is such that all conjunctive queries admit a first-order rewriting is decidable, and present a technique for solving this problem. These results have a impo...