1. A method for preparing an ontology for searching, the method comprising: compressing an ontology such that one individual in each set of semantically equivalent individuals in a same concept remains in a compressed ontology; determining semantically equivalent relations among the one individual and individuals in different concepts in the compressed ontology; determining semantically restricted relations among the one individual and other individuals in the different concepts in the compressed ontology; determining semantically equivalent concepts among the same and different concepts in the compressed ontology; determining semantically restricted relations among the same and different concepts in the compressed ontology; and constructing a semantically restricted relation graph based at least on the semantically restricted relations among the one individual and the other individuals and the semantically restricted relations among the same and different concepts, wherein a query is answered using the semantically restricted relation graph.