FOUNDATION FOR INTELLIGENT PHYSICAL AGENTS

FIPA 98 Specification

Part 12

Ontology Service

Obsolete

Publication date: 23^rd October 1998

Geneva, Switzerland

This is one part of the first version of the FIPA 98 Specification as released in October 1998.
The latest version of this document may be found on the FIPA web site:

http://www.fipa.org

Comments and questions regarding this document and the specifications therein should be addressed to:
Specs@fipa.org

It is planned to introduce a web-based mechanism for submitting comments to the specifications.
Please refer to the web site for FIPA's latest policy and procedure for dealing with issues regarding the specification.

Notice

Use of the technologies described in this specification may infringe patents, copyrights or other intellectual property rights of FIPA Members and non-members. Nothing in this specification should be construed as granting permission to use any of the technologies described. Anyone planning to make use of technology covered by the intellectual property rights of others should first obtain permission from the holder(s) of the rights. FIPA strongly encourages anyone implementing any part of this specification to determine first whether part(s) sought to be implemented are covered by the intellectual property of others, and, if so, to obtain appropriate licenses or other permission from the holder(s) of such intellectual property prior to implementation. This FIPA 98 Specification is subject to change without notice. Neither FIPA nor any of its Members accept any responsibility whatsoever for damages or liability, direct or consequential, which may result from the use of this specification.

Contents

1 Scope.......................................................................................................................................... 3

2 Normative reference(s)................................................................................................................. 3

3 Terms and definitions................................................................................................................. 3

4 Symbols (and abbreviated terms)................................................................................................ 3

5 Overview..................................................................................................................................... 3

5.1 Rationale for having explicit ontologies...................................................................................... 3

5.2 Possible benefits for applications............................................................................................... 3

5.3 Some sample scenarios illustrating offered features................................................................... 3

5.3.1 Scenario 1 – Querying the OA for definition of terms................................................................... 3

5.3.2 Scenario 2 – selecting a shared ontology.................................................................................... 3

5.3.3 Scenario 3 – testing equivalence................................................................................................. 3

5.3.4 Scenario 4 – finding ontologies................................................................................................... 3

5.3.5 Scenario 5 - translation of terms.................................................................................................. 3

6 Specification of the Ontology Service.......................................................................................... 3

6.1 Reference Model.......................................................................................................................... 3

6.1.1 Services provided by the Ontology Agent.................................................................................... 3

6.2 Naming and referring Ontologies................................................................................................ 3

6.3 Relationships between Ontologies.............................................................................................. 3

6.3.1 Level = extension..................................................................................................................... 3

6.3.2 Level = identical..................................................................................................................... 3

6.3.3 Level = equivalent................................................................................................................... 3

6.3.4 Level = weakly-translatable................................................................................................. 3

6.3.5 Level = strongly-translatable............................................................................................. 3

6.3.6 Level = approx-translatable................................................................................................. 3

6.3.7 General properties....................................................................................................................... 3

6.4 Registration of the Ontology Agent with the DF........................................................................... 3

6.4.1 Querying the DF.......................................................................................................................... 3

6.5 FIPA Knowledge Model and FIPA meta-ontology......................................................................... 3

6.5.1 Symbols in the FIPA-meta-ontology............................................................................................ 3

6.6 Responsibilities, Actions and Predicates Supported by the Ontology Agent................................ 3

6.6.1 Responsibilities of the Ontology Agent....................................................................................... 3

6.6.2 Assertion..................................................................................................................................... 3

6.6.3 Retraction.................................................................................................................................... 3

6.6.4 Query.......................................................................................................................................... 3

6.6.5 Modify......................................................................................................................................... 3

6.6.6 Translation of the Terms and Sentences between Ontologies...................................................... 3

6.6.7 Error handling............................................................................................................................. 3

6.7 Interaction Protocol to agree on a shared ontology..................................................................... 3

6.8 FIPA-Ontol-service-Ontology....................................................................................................... 3

6.8.1 List of predicates......................................................................................................................... 3

6.8.2 List of actions............................................................................................................................. 3

6.8.3 List of objects and constant values............................................................................................. 3

7 References.................................................................................................................................. 3

Annex A (informative) Ontologies and Conceptualizations.................................................................................... 3

I. Ontologies vs. conceptualizations................................................................................................................ 3

II. A formal account of ontologies and conceptualizations.............................................................................. 3

II.1 What is a conceptualization....................................................................................................................... 3

II.2 What is an ontology................................................................................................................................... 3

III. The Ontology Integration Problem............................................................................................................. 3

IV. Basic kinds of ontologies........................................................................................................................... 3

IV.1 From top-level to application-level........................................................................................................... 3

IV.2 Shareable Ontologies and Reference Ontologies...................................................................................... 3

IV.3 Meta-level Ontologies............................................................................................................................... 3

V. References.................................................................................................................................................. 3

Annex B (informative) Guidelines to define a New Ontology ............................................................................ 3

I. Set of principles useful in the development of ontologies........................................................... 3

II. Ontology development process................................................................................................................... 3

II.1 Project Management Activities................................................................................................................... 3

II.2 Development Activities.............................................................................................................................. 3

II.4 Ontology Life Cycle................................................................................................................................... 3

III. Methodology to build ontologies................................................................................................................ 3

III.1 Specification............................................................................................................................................ 3

III.2 Knowledge acquisition............................................................................................................................. 3

III.3 Ontology and Natural Language............................................................................................................... 3

IV. References................................................................................................................................................. 3

Natural Language based Knowledge acquisition references............................................................................ 3

Foreword

The Foundation for Intelligent Physical Agents (FIPA) is a non-profit association registered in Geneva, Switzerland. FIPA’s purpose is to promote the success of emerging agent-based applications, services and equipment. This goal is pursued by making available in a timely manner, internationally agreed specifications that maximise interoperability across agent-based applications, services and equipment. This is realised through the open international collaboration of member organisations, which are companies and universities active in the agent field. FIPA intends to make the results of its activities available to all interested parties and to contribute the results of its activities to appropriate formal standards bodies.

This specification has been developed through direct involvement of the FIPA membership. The 48 members of FIPA (October 1998) represent 13 countries world-wide.

Membership in FIPA is open to any corporation and individual firm, partnership, governmental body or international organisation without restriction. By joining FIPA each member declares himself individually and collectively committed to open competition in the development of agent-based applications, services and equipment. Associate Member status is usually chosen by those entities who want to be members of FIPA without using the right to influence the precise content of the specifications through voting.

The members are not restricted in any way from designing, developing, marketing and/or procuring agent-based applications, services and equipment. Members are not bound to implement or use specific agent-based standards, recommendations and FIPA specifications by virtue of their participation in FIPA.

This specification is published as FIPA 98 specifications ver 1.0. All these parts have undergone an intense review by members as well as non-members during the past year as preliminary versions have been available on the FIPA web site. FIPA members as well as many non-members have been conducting validation trials of the FIPA 97 specification during 1998 and will continue to subject the new output to further validation during the coming months. During 1999 FIPA will publish revised versions of the current specifications and is also planning to continue work on further specifications of agent based technology.

Introduction

The FIPA specifications represent the primary output of FIPA. It is important to appreciate that these specifications have been derived from examining requirements on agent technology posed by specific industrial applications chosen by FIPA so far, and described in Parts 4, 5, 6, and 7 of the FIPA 97 specifications.

FIPA specifies the interfaces of the different components in the environment with which an agent can interact, i.e. humans, other agents, non-agent software and the physical world. FIPA produces two kinds of specifications:

· normative specifications mandating the external behavior of an agent and ensuring interoperability with other FIPA-specified subsystems;

· informative specifications of applications providing guidance to industry on the use of FIPA technologies.

In October 1997, FIPA released its first set of specifications, called FIPA 97, Version 1.0. During 1998, comments on this specification were received. Based upon these comments, parts of FIPA 97 were superseded by a second version released in October 1998, introducing minor changes only.

Furthermore, in October 1998 FIPA released a new set of specifications, called FIPA 98, version 1.0, of which this document is a part.

The following tables provide an overview of the complete set of FIPA specifications.

Sorted by part:

		*Released October 1997*	*Released October 1998*
Part		FIPA 97 Version 1.0	FIPA 97 Version 2.0	FIPA 98 Version 1.0
1	N	Agent Management	Agent Management	Agent Management Extensions
2	N	ACL	ACL
3	N	Agent Software Integration
4	I	Personal Travel Assistant
5	I	Personal Assistant
6	I	Audio Visual Entertainment & Broadcasting
7	I	Network Management & Provision
8	N			Human-Agent Interaction
10	N			Agent Security Management
11	N			Agent Management Support for Mobility
12	N			Ontology Service
13	I/M			Developer’s Guide

N == normative; I == informative; M == methodology; Italicised == superseded

Sorted by topic:

Topic	FIPA 97(Version 1.0, unless otherwise indicated)	FIPA 98 Version 1,0
Agent Management	1. Basic System (Version 2.0)	1. Extension to Basic System
		10. Agent Security Management
		11. Agent Management Support for Mobility
Agent Communication	2. Agent Communication Language (Version 2.0)	8. Human-Agent Interaction
		12. Ontology Service
Agent S/W Integration	3. Agent Software Integration
Reference Applications	4. Personal Travel Assistant
	5. Personal Assistant
	6. Audio/Visual Entertainment & Broadcasting
	7. Network Management & Provisioning

The parts of the FIPA 98 specifications are briefly described below.

Part 1 - Agent Management

This part covers agent management for inter-operable agents, and is thus primarily concerned with defining open standard interfaces for accessing agent management services. It also specifies an agent management ontology and agent platform message transport. This specification incorporates and further enhances the FIPA 97, Part 1, Version 2.0 specification. The internal design and implementation of intelligent agents and agent management infrastructure is not mandated by FIPA and is outside the scope of this part.

Part 8 – Human-Agent Interaction

This part deals with the human-agent interaction part of an agent system. It specifies two agent services: User Dialog Management Service (UDMS) and User Personalization Service (UPS). A UDMS wraps many types of software components for user interfaces allowing for ACL level of interaction between agents and human users. A UPS can maintain user models and supports their construction by either accepting explicit information about the user or by learning from observations of user behavior.

Part 10 – Agent Security Management

Security risks exist throughout agent management: during registration, agent-agent interaction, agent configuration, agent-agent platform interaction, user-agent interaction and agent mobility. The Security Management specification identifies the key security threats in agent management and specifies facilities for securing agent-agent communication via the FIPA agent platform. This specification represents the minimal set of technologies required and is complementary to the existing FIPA 97 and FIPA 98, Part 1 specifications. This part does not mandate every FIPA-compliant agent platform to support agent security management.

Part 11 – Agent Management Support for Mobility

This specification represents a normative framework for supporting software agent mobility using the FIPA agent platform. This framework represents the minimal set of technologies required and is complementary to the existing FIPA 97 and FIPA 98, Part 1 specifications. Wherever possible, it refers to existing standards in this area. The framework supports additional non-mobile agent management operations such as agent configuration. The specification does not mandate that every FIPA-compliant agent platform must support agent mobility, nor does it cover the specific requirements for agents on mobile devices with intermittent connectivity, which is covered by the scope of the existing FIPA Agent Management activity.

Part 12 – Ontology Service

This part deals with technologies enabling agents to manage explicit, declaratively represented ontologies. It specifies an ontology service provided to a community of agents by a dedicated Ontology Agent. It allows for discovering public ontologies in order to access and maintain them; translating expressions between different ontologies and/or different content languages; responding to queries for relationships between terms or between ontologies; and, facilitating identification of a shared ontology for communication between two agents.

The specification deals only with the communicative interface to such a service while internal implementation and capabilities are left to developers. The interaction protocols, communicative acts and, in general, the vocabulary that agents must adopt when using this service are defined. The specification does not mandate the storage format of ontologies, but only the way the ontology service is accessed. However, in order to specify the service, an explicit representation formalism, or meta-ontology, has been specified allowing communication of knowledge between agents.

Part 13 – FIPA 97 Developer's Guide

The Developer’s Guide is meant to be a companion document to the FIPA 97 specifications, and is intended to clarify areas of specific interest and potential confusion. Such areas include issues that span more than one of the normative parts of FIPA 97.

1 Scope

The model of agent communication in FIPA is based on the assumption that two agents, who wish to converse, share a common ontology for the domain of discourse. It ensures that the agents ascribe the same meaning to the symbols used in the message. For a given domain, designers may decide to use ontologies that are explicit, declaratively represented (and stored somewhere) or, alternatively, ontologies that are implicitly encoded with the actual software implementation of the agent themselves and thus are not formally published to an ontology service.

This Part of FIPA 98 specifications deals with technologies enabling agents to manage explicit, declaratively represented ontologies. An ontology service for a community of agents is specified for this purpose. It is required that the service be provided by a dedicated agent, hereafter called Ontology Agent (OA), whose role in the community is to provide some or all of the following services:

- discovery of public ontologies in order to access them;

- maintain (e.g. register with the DF, upload, download, and modify) a set of public ontologies;

- translate expressions between different ontologies and/or different content languages;

- respond to query for relationships between terms or between ontologies;

- facilitate the identification of a shared ontology for communication between two agents.

This specification deals only with the communicative interface to such a service while internal implementation and capabilities are left to developers. It is not mandated that every OA be able to execute all those tasks (e.g. translation between ontologies, and identification of a shared ontology are in general very difficult and not always possible to realize), but every OA must be able to participate into a communication about these tasks (possibly responding that it is not able to execute the translation task). The interface is specified at the agent communication level [1,2] as opposed to a computational API. Therefore, the specification defines the interaction protocols, the communicative acts and, in general, the vocabulary that agents must adopt when using this service.

The specification enables developers to build:

- agents that access such a service,

- agents that provide it,

- agents able to negotiate at run-time a shared ontology for communication.

The application of this specification does not prevent the existence of agents that, for a given domain, use ontologies implicitly encoded with the implementation of the agents themselves. In these cases full agent communication and understanding can still be obtained, however the services provided by the OA cannot apply to implicit encoded ontologies.

It is not intention of this document to mandate that every FIPA Agent Platform must include an Ontology Agent. However, in order to promote interoperability, if one OA exists, then it must comply with these specification. And, if the services here described are required by a specific agent platform implementation, then they must be implemented in compliance with this specification.

In order to keep the applicability of the specification as unrestricted as possible, the approach used is platform independent. In particular, this specification does not mandate the storage format of ontologies but only the way agents access an ontology service. However, in order to specify the service, an explicit representation formalism has been specified. It is the FIPA Knowledge Model, identified by the name Fipa-meta-ontology, that allows communication of knowledge between agents. As far as possible, care has been taken to integrate existing formalisms, such as RDF [5] and OKBC [3].

2 Normative reference(s)

The following normative documents contain provisions which, through reference in this text, constitute provisions of this specification. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this specification are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid specifications, term(s) and definition(s).

FIPA 1998. FIPA 97 specification – Part 1: Agent Management – version 2.0, October 1998.

FIPA 1998. FIPA 97 specification – Part 2: Agent Communication Language – version 2.0, October 1998.

Vinay K. Chaudhri Artificial Intelligence Center SRI InternationalAdam Farquhar Knowledge Systems Laboratory Stanford UniversityRichard Fikes Knowledge Systems Laboratory Stanford UniversityPeter D. Karp Artificial Intelligence Center SRI InternationalJames P. Rice Knowledge Systems Laboratory Stanford University. Open Knowledge Base Connectivity 2.0.4 - April 9, 1998. Chapter 2 – Knowledge Model.

3 Terms and definitions

For the purposes of this specification, the following terms and definitions apply:

Action

A basic construct which represents some activity which an agent may perform. A special class of actions is the communicative acts.

Agent

An Agent is the fundamental actor in a domain. It combines one or more service capabilities into a unified and integrated execution model which can include access to external software, human users and communication facilities.

Agent cloning

The process by which an agent creates a copy of itself on an agent platform.

Agent code

The set of instructions used by an agent.

Agent Communication Language (ACL)

A language with precisely defined syntax, semantics and pragmatics that is the basis of communication between independently designed and developed software agents. ACL is the primary subject of the FIPA 97 specification, part 2.

Agent Communication Channel (ACC)

The Agent Communication Channel is an agent which uses information provided by the Agent Management System to route messages between agents within the platform and to agents resident on other platforms.

Agent data

Any data associated with an agent.

Agent invocation

The process by which an agent can create another instance of an agent on an agent platform.

Agent Management System (AMS)

The Agent Management System is an agent which manages the creation, deletion, suspension, resumption, authentication and migration of agents on the agent platform and provides a “white pages” directory service for all agents resident on an agent platform. It stores the mapping between globally unique agent names (or GUID) and local transport addresses used by the platform.

Agent Platform

An Agent Platform provides an infrastructure in which agents can be deployed. An agent must be registered on a platform in order to interact with other agents on that platform or indeed other platforms. An AP consists of three capability sets ACC, AMS and default Directory Facilitator.

Agent Platform Security Manager (APSM)

An Agent Platform Security Manager is responsible for maintaining the agent platform security policy. The APSM is responsible for providing transport-level security and creating agent audit logs. The APSM negotiates the requested intra- and inter-domain security services of other APSM's in concert with the implemented distributed computing architectures, such as CORBA, COM, DCE, on behalf of an agent in its domain.

ARB Agent

An agent which provides the Agent Resource Broker (ARB) service. There must be at least one such an agent in each Agent Platform in order to allow the sharing of non-agent services.

Communicative Act

A special class of actions that correspond to the basic building blocks of dialogue between agents. A communicative act has a well-defined, declarative meaning independent of the content of any given act. CAs are modelled on speech act theory. Pragmatically, CAs are performed by an agent sending a message to another agent, using the message format described in FIPA97, part 2.

Content

That part of a communicative act which represents the domain dependent component of the communication. Note that "the content of a message" does not refer to "everything within the message, including the delimiters", as it does in some languages, but rather specifically to the domain specific component. In the ACL semantic model, a content expression may be composed from propositions, actions or IRE's.

Content Language

The content of a FIPA message refers to whatever the communicative act applies to. If, in general terms, the communicative act is considered as a sentence, the content is the grammatical object of the sentence. This content can be encoded in any language, the content language, denoted by the :language parameter of the communicative act.

Conversation

An ongoing sequence of communicative acts exchanged between two (or more) agents relating to some ongoing topic of discourse. A conversation may (perhaps implicitly) accumulate context that is used to determine the meaning of later messages in the conversation.

CORBA

Common Object Request Broker Architecture, an established standard allowing object-oriented distributed systems to communicate through the remote invocation of object methods.

Directory Facilitator

The Directory Facilitator [1] is an agent that provides a “yellow pages” directory service for the agents. It stores descriptions of the agents and the services they offer.

Explicit & Implicit

An ontology is explicit when it is specified in declarative form as a set of axioms and definitions (e.g. as a set of Ontolingua statements) that an agent can refer to (e.g. by means of an OKBC interface). An ontology is implicit, when the assumptions on the meaning of its vocabulary are only implicitly embedded in some piece of software.

Feasibility Precondition (FP)

The conditions (i.e. one or more propositions) which need be true before an agent can (plan to) execute an action.

Knowledge model

It is a specification of the set of primitives used by a certain class of representation languages. As such, a knowledge model can be considered as a meta-ontology. For instance, several ontology servers use an object oriented model of knowledge based on primitive notions like classes, frames, properties, constraints, axioms and functions. FIPA adopts for the specification of these notions the OKBC version 2.0.4 Knowledge Model, which is called FIPA-meta-ontology or FIPA knowledge model.

Illocutionary effect

See speech act theory.

Knowledge Querying and Manipulation Language (KQML)

A de facto (but widely used) specification of a language for inter-agent communication. In practice, several implementations and variations exist.

Local Agent Platform

The Local Agent Platform is the AP to which an agent is attached and which represents an ultimate destination for messages directed to that agent.

Message

An individual unit of communication between two or more agents. A message corresponds to a communicative act, in the sense that a message encodes the communicative act for reliable transmission between agents. Note that communicative acts can be recursively composed, so while the outermost act is directly encoded by the message, taken as a whole a given message may represent multiple individual communicative acts.

Message content

See content.

Message transport service

The message transport service is an abstract service provided by the agent management platform to which the agent is (currently) attached. The message transport service provides for the reliable and timely delivery of messages to their destination agents, and also provides a mapping from agent logical names to physical transport addresses.

Meta-ontology

For allowing a FIPA agent to communicate through ACL messages aboutontologies, it is necessary to describe the concepts used to speak about anontology. This description is called the meta-ontology. It is an ontologyitself as it provides the ontology to refer to another ontology. Therefore,the meta-ontology should be powerful enough to deal with all potentiallyavailable ontologies and make explicit, at least informally, these concepts.

Mobile agent

An agent that is not reliant upon the agent platform where it began executing and can subsequently transport itself between agent platforms.

Mobility

The property or characteristic of an agent that allows it to travel between agent platforms.

Ontology

An ontology is an explicit specification of the structure of a certain domain (e.g. e-commerce, sport, …). For the practical goals of FIPA (that is enabling development and deployment of inter-operable agent-based applications), this includes a vocabulary (i.e. a list of logical constants and predicate symbols) for referring to the subject area, and a set of logical statements expressing the constraints existing in the domain and restricting the interpretation of the vocabulary. Ontologies therefore provide a vocabulary for representing and communicating knowledge about some topic and a set of relationships and properties that hold for the entities denoted by that vocabulary.

Ontology Agent

An agent that provides the Ontology Service specified in this specification. The main objective of the Ontology Agent is to offer to FIPA agents a unified view of the services offered by the different ontology servers. Its second objective is to allow an ontology server to be known by FIPA agents. Moreover some ontology agents can provide the agents with services such as translation facilities. Like any other FIPA agent, the ontology agent has to be registered to the DF and to provide the DF with the published ontologies and available services.

Ontology Name

The ontologies referred to by the agents can be provided by different ontology servers. Consequently, these ontology names are constructed from: the OA name, and the ontology logical name (given by the ontology designer e.g. “car “).

Ontology Server

Provider of an Ontology Service, not necessarily in the FIPA domain, or FIPA-compliant. Examples of ontology servers already existing outside FIPA are: Ontolingua, XML/RDF ontology servers, ODL databases ontologies servers. Access to the services provided by these ontologies servers are based on various APIs such as the OKBC interface, the ODL interface or HTTP.

Ontology sharing problem

The problem of ensuring that two agents that wish to converse do, in fact, share a common ontology for the domain of discourse. Minimally, agents should be able to discover whether or not they share a mutual understanding of the domain constants.

Perlocutionary Effect

See speech act theory.

Personalization

An agent’s ability to take individual preferences and characteristics of users into account and adapt its behavior to these factors.

Proposition

A statement which can be either true or false. A closed proposition is one which contains no variables, other than those defined within the scope of a quantifier.

Protocol

A common pattern of conversations used to perform some generally useful task. The protocol is often used to facilitate a simplification of the computational machinery needed to support a given dialogue task between two agents. Throughout this document, we reserve protocol to refer to dialogue patterns between agents, and networking protocol to refer to underlying transport mechanisms such as TCP/IP.

Rational Effect (RE)

The rational effect of an action is a representation of the effect that an agent can expect to occur as a result of the action being performed. In particular, the rational effect of a communicative act is the perlocutionary effect an agent can expect the CA to have on a recipient agent. Note that the recipient is not bound to ensure that the expected effect comes about; indeed it may be impossible for it to do so. Thus an agent may use its knowledge of the rational effect in order to plan an action, but it is not entitled to believe that the rational effect necessarily holds having performed the act.

Software Service

An instantiation of a connection to a software system.

Software System

A software entity which is not conformant to the FIPA Agent Management specification.

Speech Act

The notion of a speech act is derived from the linguistic analysis of human communication. It is based on the idea that with language the speaker not only makes statements, but also performs actions, e.g. a request or an assertion. In this context, a verb denoting a speech act, is called a performative, since saying it makes it so. See FIPA97, part 2 for more details.

Speech Act Theory

A theory of communications which is used as the basis for ACL. Speech act theory is derived from the linguistic analysis of human communication. It is based on the idea that with language the speaker not only makes statements, but also performs actions. A speech act can be put in a stylised form that begins "I hereby request …" or "I hereby declare …". In this form the verb is called the performative, since saying it makes it so. Verbs that cannot be put into this form are not speech acts, for example "I hereby solve this equation" does not actually solve the equation.

Stationary agent

An agent that executes only upon the agent platform where it begins executing and is reliant upon it.

TCP/IP

A networking protocol used to establish connections and transmit data between hosts

User Agent

An agent which interacts with a human user.

User Dialog Management Service

An agent service in order for FIPA agents to interact with human users; by converting ACL into media/formats which human users can understand and vice versa, managing the communication channel between agents and users, and identifying users interacting with agents.

User ID

An identifier for a real user.

User Model

A user model contains assumptions about user preferences, capabilities, skills, knowledge, etc, which may be acquired by inductive processing based on observations about the user. User models normally contain knowledge bases which are directly manipulated and administered.

User Personalization Service

An agent service that offers abilities to support personalization, e.g. by maintaining user profiles or forming complex user models by learning from observations of user behavior.

Wrapper Agent

An agent which provides the FIPA-WRAPPER service to an agent domain on the Internet.

4 Symbols (and abbreviated terms)

ACC	Agent Communication Channel
ACL	Agent Communication Language
AMS	Agent Management System
API	Application Programming Interface
CA	Communicative Act
DB	Data Base
DF	Directory Facilitator
EBNF	Extended Backus Naur Form
FIPA	Foundation for Intelligent Physical Agents
GUID	Global Unique Identifier
HTTP	Hyper-Text Transfer/Transmission Protocol
IRE	Identifying Referring Expression
KBS	Knowledge Base System
KIF	Knowledge Interchange Format
OA	Ontology Agent
ODL	Object Definition Language
OKBC	Open Knowledge Base Connectivity
OQL	Object Query Language
RDF	Resource Description Framework
SL	Semantic Language
TCP/IP	Transmission Control Protocol / Internet Protocol
TKB	Terminological Knowledge Base
XML	Extensible Markup Language

5 Overview

An Ontology Agent (OA) is an agent that provides access to one or more ontology servers and that provides the ontology services, as specified in this specification, to an agent community. As well as all the other agents, the OA registers its service with the DF (see section 6.4) and it is identified by the keyword FIPA-OA for the value of :agent-type. It also registers the list of maintained ontologies and their translation capabilities in order to allow agents to query the DF (see section 6.4.1) for the specific OA that manages a specific ontology.

Every agent can then request the services of the OA by using the communicative interface specified in section 6. In particular, they can request to define, modify or remove terms and definitions of the ontology; they can request to translate expressions between two ontologies for which there exists a mapping; they can query for definitions, or relationships between terms or between ontologies; finally, they can request to find a shared ontology for communication with another agent. Even if any agent requests one of the above services, the OA reserves the right to refuse the request.

The realization of this communication obviously needs an agreement on the language to communicate facts about ontologies. This is described in section 6.2 where the subsumed knowledge model and the FIPA meta-ontology is specified. It describes the primitives, and normatively define their names, used in the communication, like concepts, attributes, relations, … It must be noticed that this specification is neutral in respect to the language used to store and represent the ontology (e.g. RDF, KIF, ODL, …), while it only specifies the language to communicate about ontologies.

Section 6.7 specifies the interaction protocol to be used by agents to agree on a shared ontology for communication.

The document concludes with two informative annexes. Annex A gives a clear definition of what is intended with the term ontology and, in particular, what is the difference between a conceptualization, an ontology, and a