A method is provided for an application program interface (API) to interface with an ontology store storing a plurality of modifiable ontology models having associated dynamic definitions associated that define classes of the associated ontology model and relationships between the respective classes and that is modifiable over time. The method includes receiving from a requesting entity a request that specifies an ontology model and one or more parameters defining attributes of an instantiated ontology object, accessing the ontology store, identifying an ontology model in the ontology store that corresponds to the ontology model specified, and manipulating the identified ontology model based on its one or more parameters. The method further includes generating a semantics query for accessing the identified ontology model based on the one or more parameters specified in the request, submitting the semantics query to and receiving query results from the ontology store, and returning the query results to the requesting entity.