Abstract
Combining knowledge representation and reasoning formalisms is an important and challenging task. It is important because non-trivial AI applications often comprise different aspects of the world, thus requiring suitable combinations of available formalisms modeling each of these aspects. It is challenging because the computational behavior of the resulting hybrids is often much worse than the behavior of their components. In this paper, we propose a new combination method which is computationally robust in the sense that the combination of decidable formalisms is again decidable, and which, nonetheless, allows non-trivial interactions between the combined components. The new method, called ε-connection, is defined in terms of abstract description systems (ADSs), a common generalization of description logics, many logics of time and space, as well as modal and epistemic logics. The basic idea of ε-connections is that the interpretation domains of n combined systems are disjoint, and that these domains are connected by means of n-ary 'link relations'. We define several natural variants of ε-connections and study in-depth the transfer of decidability from the component systems to their ε-connections. © 2004 Elsevier B.V. All rights reserved.