 The use of ontologies in supporting semantic interoperability is to provide a fixed set of concepts whose meanings and relations are stable and can be agreed to by users.The task of determining which terms in which contexts (each database is a different context) is then separated from the task of creating the ontology, and must be taken up by the designer of a database, or the designer of a form for data entry, or the developer of a program for language understanding.When the meaning of a word used in some interoperable context is changed, then to preserve interoperability it is necessary to change the pointer to the ontology element(s) that specifies the meaning of that word.