FOUNDATION FOR INTELLIGENT PHYSICAL AGENTS

FIPA Communicative Act Library Specification

Document title	FIPA Communicative Act Library Specification
Document number	XC00037G	Document source	FIPA TC C
Document status	Experimental	Date of this status	2001/01/29
Supersedes	FIPA00003, FIPA00038, FIPA00039, FIPA00040, FIPA00041, FIPA00042, FIPA00043, FIPA00044, FIPA00045, FIPA00046, FIPA00047, FIPA00048, FIPA00049, FIPA00050, FIPA00051, FIPA00052, FIPA00053, FIPA00054, FIPA00055, FIPA00056, FIPA00057, FIPA00058, FIPA00059, FIPA00060
Contact	fab@fipa.org
Change history
2001/01/29	Approved for Experimental

Geneva, Switzerland

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 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.

Foreword

The Foundation for Intelligent Physical Agents (FIPA) is an international organization that is dedicated to promoting the industry of intelligent agents by openly developing specifications supporting interoperability among agents and agent-based applications. This occurs through open collaboration among its member organizations, which are companies and universities that are active in the field of agents. FIPA makes the results of its activities available to all interested parties and intends to contribute its results to the appropriate formal standards bodies.

The members of FIPA are individually and collectively committed to open competition in the development of agent-based applications, services and equipment. Membership in FIPA is open to any corporation and individual firm, partnership, governmental body or international organization without restriction. In particular, members are not bound to implement or use specific agent-based standards, recommendations and FIPA specifications by virtue of their participation in FIPA.

The FIPA specifications are developed through direct involvement of the FIPA membership. The status of a specification can be either Preliminary, Experimental, Standard, Deprecated or Obsolete. More detail about the process of specification may be found in the FIPA Procedures for Technical Work. A complete overview of the FIPA specifications and their current status may be found in the FIPA List of Specifications. A list of terms and abbreviations used in the FIPA specifications may be found in the FIPA Glossary.

FIPA is a non-profit association registered in Geneva, Switzerland. As of January 2000, the 56 members of FIPA represented 17 countries worldwide. Further information about FIPA as an organization, membership information, FIPA specifications and upcoming meetings may be found at http://www.fipa.org/.

Contents

1 Introduction. 1

2 Overview. 2

2.1 Status of a FIPA-Compliant Communicative Act 2

2.2 FIPA Communicative Act Library Maintenance. 2

2.3 Inclusion Criteria. 3

3 FIPA Communicative Acts. 4

3.1 Accept Proposal 4

3.2 Agree. 5

3.3 Cancel 6

3.4 Call for Proposal 7

3.11 Not Understood. 14

3.18 Reject Proposal 24

3.19 Request 25

3.20 Request When. 26

3.21 Request Whenever 27

3.22 Subscribe. 28

4 References. 29

5 Informative Annex A — Formal Basis of ACL Semantics. 30

5.1 Introduction to the Formal Model 30

5.2 The Semantic Language. 31

5.2.1 Basis of the Semantic Language Formalism.. 31

5.2.2 Abbreviations. 32

5.3 Underlying Semantic Model 33

5.3.7 Note on the Use of Symbols in Formulae. 35

5.3.8 Supporting Definitions. 35

5.4 Primitive Communicative Acts. 35

5.4.1 The Assertive Inform.. 35

5.4.2 The Directive Request 36

5.4.3 Confirming an Uncertain Proposition: Confirm.. 36

5.4.4 Contradicting Knowledge: Disconfirm.. 36

5.5 Composite Communicative Acts. 37

5.5.1 The Closed Question Case. 37

5.5.2 The Query If Act 38

5.5.3 The Confirm/Disconfirm Question Act 38

5.5.4 The Open Question Case. 39

5.6 Inter-Agent Communication Plans. 40

1 Introduction

This document contains specifications for structuring the FIPA Communicative Act Library (FIPA CAL) including: status of a FIPA-compliant communicative act, maintenance of the library and inclusion criteria.

This document is primarily concerned with defining the structure of the FIPA CAL and the requirements for a proposed communicative act to be included in the library. The elements of the library are listed in this document.

This document also contains the formal basis of FIPA ACL semantics in the annex for the semantic characterization of each FIPA communicative act.

2 Overview

This document focuses on the organization, structure and status of the FIPA Communicative Act Library, FIPA CAL and discusses the main requirements that a communicative act must satisfy in order to be FIPA-compliant.

The objectives of standardizing and defining a library of FIPA compliant communicative acts are:

· To help ensure interoperability by providing a standard set of composite and macro communicative acts, derived from the FIPA primitive communicative acts,

· To facilitate the reuse of composite and macro communicative acts, and,

· To provide a well-defined process for maintaining a set of communicative acts and act labels for use in the FIPA ACL.

In the following, we present the basic principles of the FIPA CAL. These principles help to guarantee that the CAL is stable, that there are public rules for the inclusion and maintenance of the CAL and that developers seeking communicative acts for their applications can use the CAL.

2.1 Status of a FIPA-Compliant Communicative Act

The definition of a communicative act belonging to the FIPA CAL is normative. That is, if a given agent implements one of the acts in the FIPA CAL, then it must implement that act in accordance with the semantic definition in the FIPA CAL. However, FIPA-compliant agents are not required to implement any of the FIPA CAL languages, except the not-understood composite act.

By collecting communicative act definitions in a single, publicly accessible registry, the FIPA CAL facilitates the use of standardized Communicative Acts by agents developed in different contexts. It also provides a greater incentive to developers to make any privately developed communicative acts generally available.

The name assigned to a proposed communicative act must uniquely identify which communicative act is used within a FIPA ACL message. It must not conflict with any names currently in the library, and must be an English word or abbreviation that is suggestive of the semantics. The FIPA Agent Communication Technical Committee is the initial judge of the suitability of a name.

FIPA is responsible for maintaining a consistent list of approved and proposed communicative act names and for making this list publicly available to FIPA members and non-members. This list is derived from the FIPA Communicative Act Library.

In addition to the semantic characterization and descriptive information that is required, each Communicative Act in the FIPA CAL may specify additional information, such as stability information, versioning, contact information, different support levels, etc.

2.2 FIPA Communicative Act Library Maintenance

The most effective way of maintaining the FIPA Communicative Act Library is through the use of the communicative acts themselves by different agent developers. This is the most direct way of discovering possible bugs, errors, inconsistencies, weaknesses, possible improvements, as well as capabilities, strengths, efficiency etc. In order to collect feedback on the communicative acts in the library and to promote further research, FIPA encourages coordination between agent language designers, agent developers, and FIPA members.

FIPA will designate a Technical Committee to maintain the FIPA CAL. The FIPA CAL will be managed by this technical committee, which will be responsible for the following items:

· Collecting feedback and the comments about communicative acts in the FIPA CAL. Depending on interest, the technical committee may organize more specific Working Groups. These groups would be responsible for maintaining public lists referring to projects and people who are currently working on different communicative acts.

· Inviting contributions in various forms: e-mail comments, written reports, papers, technical documents, and so forth. The current email address of the technical committee is specified on the first page of this document.

· All technical committee members will be notified about contributions, comments or proposed changes and should be able to access them.

· The proposed updates to the FIPA CAL must be discussed and approved during an official FIPA meeting, in order that the FIPA community may be involved with and informed of all of the FIPA approved communicative acts in the library

· In the future, FIPA intends to supply templates (publicly accessible from the FIPA web site) in order to facilitate submission of candidate communicative acts to the FIPA CAL, and to ensure that agent language developers understand and can easily satisfy the requirements for the submission of a new communicative act to the FIPA CAL.

2.3 Inclusion Criteria

In order to populate the FIPA CAL, it is necessary to set some fundamental guidelines for the selection of specific communicative acts.

The minimal criteria that must be satisfied for a communicative act to be included in the FIPA CAL are:

· A summary of the candidate act's semantic force and content type are required.

· A detailed natural language description of the act and its consequences are required.

· A formal model, written in SL, of the act's semantics, its formal preconditions, and its rational effects is required.

· Examples of the usage of the new communicative act are required.

· Substantial and clear documentation must be provided. This means that the proposal must be already well structured. FIPA members are in no way responsible for translating submitted communicative acts into an acceptable form. See the form of the acts in the library for a sample.

· The utility of such a new communicative act should be made clear. In particular, it should be clear that the need it solves is reasonably general, and that this need would be cumbersome to meet by combining existing communicative acts.

FIPA does not enforce the use of any particular communicative act, except for the case of not-understood, and those acts which are required to meet the agent management needs of the agent.

3 FIPA Communicative Acts

3.1 Accept Proposal

Summary	The action of accepting a previously submitted proposal to perform an action.
Message Content	A tuple consisting of an action expression denoting the action to be done, and a proposition giving the conditions of the agreement.
Description	Accept-proposal is a general-purpose acceptance of a proposal that was previously submitted (typically through a propose act). The agent sending the acceptance informs the receiver that it intends that (at some point in the future) the receiving agent will perform the action, once the given precondition is, or becomes, true. The proposition given as part of the acceptance indicates the preconditions that the agent is attaching to the acceptance. A typical use of this is to finalize the details of a deal in some protocol. For example, a previous offer to "hold a meeting anytime on Tuesday" might be accepted with an additional condition that the time of the meeting is 11.00. Note for future extension: an agent may intend that an action become done without necessarily intending the precondition. For example, during negotiation about a given task, the negotiating parties may not unequivocally intend their opening bids: agent a may bid a price p as a precondition, but be prepared to accept price p'.
Formal Model	<i, accept-proposal (j, <j, act>, f))> º <i, inform (j, I_i Done (<j, act>, f))> FP: B_i a Ù ØBi (Bifj a Ú Uifj a) RE: Bj a Where: a = Ii Done (<j, act>, f)
Example	Agent i informs j that it accepts an offer from j to stream a given multimedia title to channel 19 when the customer is ready. Agent i will inform j of this fact when appropriate. (accept-proposal :sender (agent-identifier :name i) :receiver (set (agent-identifier :name j)) :in-reply-to bid089 :content ((action (agent-identifier :name j) (stream-content movie1234 19)) (B (agent-identifier :name j) (ready customer78))) :language FIPA-SL)

3.2 Agree

Summary	The action of agreeing to perform some action, possibly in the future.
Message Content	A tuple, consisting of an action expression denoting the action to be done, and a proposition giving the conditions of the agreement.
Description