1. A method for building an automated assistant, the method comprising: registering a service for use in conjunction with an active ontology by specifying at least one of: one or more active processing elements that the service can accept; and one or more active processing elements that the service cannot accept; wherein: the active ontology comprises a plurality of active processing elements; the registering is performed using a processor; and the active ontology filters requests for services to the service in accordance with the one or more active processing elements specified by the service.