To allow agents to talk about knowledge and about ontologies, for instance to query for the definition of a concept or to define a new concept, a standard meta-ontology and knowledge model is necessary. This meta-ontology and knowledge model must be able to describe the primitives like concepts, attributes or relations. The ontology proposed for FIPA agents (and thus also for the ontology agent) is the frame-based OKBC Knowledge Model.
FIPA-meta-ontology based on OKBC Knowledge Model is
defined to describe ontologies. This ontology must be used by
an agent when it talks about ontologies. Ontology
FIPA-ontol-service-ontology must be used when requesting
services of an ontology agent. This
ontology extends the basic
FIPA-meta-ontology by symbols enabling
manipulation with ontologies. These ontologies are described in a tabular form
in the natural language explanation in the FIPA Ontology Service Specification.
In an open environment agents may benefit from knowing the existence of some relationships between ontologies, for example to decide if and how to communicate with other agents. In the agent community, the ontology agent has the most adequate role to know that. It can be then queried for the information about such relationships and it can use that for translation or for facilitating the selection of a shared ontology for agent communication. In the FIPA specification the relations as described in the section about relations between ontologies are proposed. The ontology agent is not required to determine these relationships, but should be able to able to maintain database of these relationships.
FIPA-ontol-service-ontology ontology is an ontology that an
ontology agent must understand and that is used to express actions and
predicates to be handled by ontology agent. It extends the base
FIPA-meta-ontology and its main elements are summarized in the table below.
An action can be
CANCELed using FIPA ACL communicative
act. For querying, the
QUERY-REF communicative acts are
|action||assert|| Assert a predicate to ontology specified in the ontology slot of the ACL message.|
The predicate to be asserted is described using the FIPA-Meta-Ontology.
|action||retract||Retract a predicate from ontology (inverse to assert).|
|action||translate|| Translate an expression between ontologies. |
The expression to be translated is specified together with the source and the requested target ontology.
|predicate||ontol-relationship||Expresses a relationship between ontologies. Possible relations were described earlier.|
Main elements of the