We describe the state of the art in the area of core computation for data exchange. Two main approaches are considered: post-processing core computation, applied to a canonical universal solution constructed by chasing a given schema mapping, and direct core computation, where the mapping is first rewritten in order to create core universal solutions by chasing it. 1998 ACM Subject Classificati...

We investigate the implication problem for constrained tuple-generating dependencies (CTGDs), the extension of tuple-and equality-generating dependencies that permits expression of semantic relations (constraints) on variables. The implication problem is central to identifying redundant integrity constraints, checking integrity constraints on constraint databases, detecting the independence of ...

Both simple and hybrid genetic algorithms encounter difficulties when presented with a function which has multiple values. Similarly, changing environments or functions which change rapidly present other problems. This paper presents an algorithm that is capable of coping with both of these scenarios: it can accommodate multiple solutions simultaneously and can track changes in optima efficient...

We explored the frequency of commencing opiate use by "chasing the dragon" to "come down" off Ecstasy and the stability of heroin smoking in young opiate takers by assessing 102 subjects in Dublin using a semistructured interview. Ninety-two subjects had used Ecstasy. Of these, 68 reported "chasing" to "come down" off Ecstasy at some point in their history and were found to have used Ecstasy mo...

Humans tend to perceive inanimate objects as animate based on simple motion cues. So far this perceptual bias has been studied mostly in humans by utilizing two-dimensional video and interactive displays. Considering its importance for survival, the perception of animacy is probably also widespread among animals, however two-dimensional displays are not necessarily the best approach to study th...