1. A computer implemented method for supporting semantic matching queries in a Structured Query Language/eXtensible Markup Language (SQL/XML) database management system (DBMS) with native XML support, having a given relational database, the computer performing steps comprising: storing transitive relationships R T of a given ontology which is not in a native XML system as an ontology relational database in the DBMS, where a relation r is transitive if the relation r between elements A and B of the ontology in combination with the relation r between elements B and C of the ontology implies the relation r between elements A and C of the ontology, all such relations r of the ontology comprising a set R of transitive relationship instances where RεR T , wherein the transitive relationships R T of ontology data are stored as XML documents having table entries for each set of transitive relationships R, each being a tree mapping of hierarchical ontology data, each of the tree mappings being a specific tuple storing all instances of the corresponding transitive relation and being searchable in SQL/XML by using native XML support, without precomputed transitive closure tables that are rebuilt when the ontology is updated; and searching the combined given relational database and the ontology relational database using SQL/XML search operators supported by the DBMS.