In information-integration systems, sources have diverse and limited query capabilities. In a recent paper [LC00], we showed that sources not mentioned in a query can contribute to the query result by providing useful bindings. We studied connection queries, where each connection query is a natural join of distinct source views with the necessary selection and projection. Some optimization prob...

While the issue on Direct Containment Heating (DCH) was resolved for US reactor plants in the 1990s it was found that the consequences of DCH processes are strongly dependent on the reactor cavity configuration. Therefore, an experimental and analytical program was started in 1998 to investigate melt ejection scenarios for typical German and European reactor designs. Six experiments have been p...

In object-oriented systems, it is often the case that an object will have an attribute whose value identiies (points or refers to) some other object in the system so that the identiied object can be sent messages. In general, there is no assumed geometric notion of relative location associated with such object references, e.g. when a bank customer references a bank account for the purposes of d...

Containment of monadic datalog programs over data trees (labelled trees with an equivalence relation) is undecidable. Recently, decidability was shown for two incomparable fragments: downward programs, which never move up from visited tree nodes, and linear childonly programs, which have at most one intensional predicate per rule and do not use descendant relation. As di erent as the fragments ...

The problem of answering queries using views has been studied extensively due to its relevance in a wide variety of data-management applications. In these applications, we often need to select a subset of views to maintain due to limited resources. In this paper, we show that traditional query containment is not a good basis for deciding whether or not a view should be selected. Instead, we sho...

The containment problem of Datalog queries is well knownto be undecidable. There are, however, several Datalog frag-ments for which containment is known to be decidable, mostnotably monadic Datalog and several “regular” query lan-guages on graphs. Monadically Defined Queries (MQs) havebeen introduced recently as a joint generalization of thesequery languages.In this ...

The development of artificial general intelligence is considered by many to be inevitable. What such intelligence does after becoming aware is not so certain. To that end, research suggests that the likelihood of artificial general intelligence becoming hostile to humans is significant enough to warrant inquiry into methods to limit such potential. Thus, containment of artificial general intell...

Many efforts have been dedicated to identify restrictions on ontologies expressed as tuple-generating dependencies (tgds), a.k.a. existential rules, that lead to the decidability for the problem of answering ontology-mediated queries (OMQs). This has given rise to three families of formalisms: guarded, non-recursive, and sticky sets of tgds. In this work, we study the containment problem for OM...

In this paper we introduce an approach that allows to handle the containment problem for the fragment XP(/,//,[ ],∗) of XPath. Using rewriting techniques we define a necessary and sufficient condition for pattern containment. This rewrite view is then adapted to query evaluation on XML documents, and remains valid even if the documents are given in a compressed form, as dags.