© 2000 by Oxford University Press
Representation, reasoning, and relational structures: a hybrid logic manifesto
Computerlinguistik, Universität des Saarlandes, 66041 Saarbrücken, Germany E-mail: patrick@coli.uni-sb.de
This paper is about the good side of modal logic, the bad side of modal logic, and how hybrid logic takes the good and fixes the bad.
In essence, modal logic is a simple formalism for working with relational structures (or multigraphs). But modal logic has no mechanism for referring to or reasoning about the individual nodes in such structures, and this lessens its effectiveness as a representation formalism. In their simplest form, hybrid logics are upgraded modal logics in which reference to individual nodes is possible.
But hybrid logic is a rather unusual modal upgrade. It pushes one simple idea as far as it will go: represent all information as formulas. This turns out to be the key needed to draw together a surprisingly diverse range of work (for example, feature logic, description logic and labelled deduction). Moreover, it displays a number of knowledge representation issues in a new light, notably the importance of sorting.
Key Words: Labelled deduction, description logic, feature logic, hybrid logic, modal logic, sorted modal logic, temporal logic, nominals, knowledge representation, relational structures