1. A method of measuring similarity between instances in an ontology for use in an information retrieval system, the method comprising the steps of: obtaining a set of instances from the ontology; computing at least one of the following similarity metrics for the set of instances: a first metric that measures similarity between instances in the set of instances with respect to ontology concepts to which the instances belong; a second metric which measures similarity between instances in the set of instances where the instances are subjects in statements involving a given ontology property; and a third metric which measures similarity between instances in the set of instances where the instances are objects in statements involving a given ontology property; and storing at least one taxonomy induced by the at least one computed similarity metric, wherein the at least one induced taxonomy is usable for responding to requests submitted to an information retrieval system.