Improved information processing techniques for measuring similarity between instances in an ontology are disclosed. For example, a method of measuring similarity between instances in an ontology for use in an information retrieval system includes the following steps. A set of instances from the ontology is obtained. At least one of the following similarity metrics for the set of instances is computed: (i) a first metric that measures similarity between instances in the set of instances with respect to ontology concepts to which the instances belong; (ii) 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 (iii) 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. At least one taxonomy induced by the at least one computed similarity metric is stored, wherein the at least one induced taxonomy is usable for responding to requests submitted to an information retrieval system. When two or more of the first metric, the second metric and the third metric are computed, and two or more induced taxonomies corresponding to the two or more computed similarity metrics are stored, the method may include merging the two or more induced taxonomies to form a combined taxonomy, wherein the combined taxonomy is usable for responding to requests submitted to an information retrieval system.