S.: Relativizing concept descriptions to comparison classes

Abstract. Context-sensitivity has been for long a subject of study in linguistics, logic and computer science. Recently the problem of repre-senting and reasoning with contextual knowledge has been brought up in the research on the Semantic Web. In this paper we introduce a conserva-tive extension to the Description Logic ALC which supports representa-tion of ontologies containing relative terms, such as ‘big ’ or ‘tall’, whose meaning depends on the reference to a particular comparison class (con-text). We specify the syntax and semantics of the language and present a sound and complete tableau decision procedure.