Agent communication language

Structured negotiation is proposed as a new method through which collaborating agents can seek consensus on the apportionment of tasks and resources. The approach draws on research in collaborative planning and human dialog understanding: agent i n teractions are organized in a manner that re ects the structure of a shared plan. Negotiations are incremental and interleaved with the shared planning process while communications supporting negotiations are made e cient b y d r a wing on knowledge of a prevailing context. Agent proposals to team members are annotated with causal information that compactly expresses relationships between new proposals and the current c o n text. Normative guidelines for proposal generation further restrict communications of ancillary information to only those fragments that represent departures from the norm. Finally, a set of interpretation rules allows agents to infer information not explicitly communicated. Categories and Subject Descriptors I.2.11 Computing Methodologies]: Arti cial Intelligence|

In this paper we propose an approach to 3D agent-based virtual communities, in which autonomous agents are participants in VRML-based virtual worlds to enhance the interaction with users or serve as intelligent navigation assistants. In addition, an agent communication language (ACL) is designed as a high level communication facility, in particular for the realization of shared objects in virtual communities. As a typical example of 3D agent-based virtual communities, a VRML-based multi-user soccer game has been developed and implemented in the distributed logic programming language DLP. We discuss how DLP can be used for the implementation of 3D agent-based virtual communities.

With the rapid technological development particularly in the computer industry, many computer programming languages are being developed with many computer programs written in these languages. Writing good programs takes time and effort. It is therefore necessary that programs once written should be able to work together (interoperate) with each other so that a program written in one language can benefit from the advantages that may be associated with another program written in another language. One of the problems with interoperation of programs is the heterogeneity of the programs. This is because programs are written by different people, at different times, in different languages and with different interfaces. Agent-base Software Engineering is an attempt to facilitate the creation of software products that can easily interoperate in such settings. In Agent-base Software Engineering, programs are written as software agents (software components) that communicate with each other by exchanging messages through a communication language. For a successful communication in such heterogeneous environments, the agents have to share knowledge with each other. The aim of this tutorial is to discuss agent communication and knowledge sharing. A discussion about agent communication, methods of agent communication, agent communication languages, content languages and knowledge sharing between agents is presented together with constraints that may inhibit successful knowledge sharing and agent communication.

The Connectionist Model Transfer (CMT) framework was proposed to allow an agent the ability to instantiate and execute neural networks received from other agents in order to maintain its learning or classi cation performance in a dynamic environment. One limitation of the CMT framework was that it assumed the existence of at least one network in the system that embodied the classication mappings required to exhibit satisfactory classi cation performance for each situation that an agent might encounter. In some cases, however, an agent required a single network that embodied classi cation mappings of several existing networks in order to maintain its performance. In such cases, a new network was manually trained and submitted to the system. In this paper, we extend the CMT framework for facilitating the dynamic merging of distributed networks. This extension allows agents to utilize new, automatically trained networks that embody the classi cation mappings of several distributed, and...

The paper presents architecture of a personalized distance learning system based on multiagent technology and ontological modelling of students' profiles. Delocalization of a student data in the system is achieved by software agents, which assumed to be distributed at different platforms. These platforms operate as separate Web services and use the ACL (Agent Communication Language) for the data transfer. In this paper the algorithm is proposed, according to which the Multiagent Ontological System for Personalized Distance Learning (MOSPDL) solves the tasks of distant learning process automation, which assume utilization of the ontological models of students' and learning resources' profiles.

is one of seven departments that make up the School of Business at the University of Otago. The department offers courses of study leading to a major in Information Science within the BCom, BA and BSc degrees. In addition to undergraduate teaching, the department is also strongly involved in postgraduate research programmes leading to MCom, MA, MSc and PhD degrees. Research projects in spatial information processing, connectionist-based information systems, software engineering and software development, information engineering and database, software metrics, distributed information systems, multimedia information systems and information systems security are particularly well supported. The views expressed in this paper are not necessarily those of the department as a whole. The accuracy of the information presented in this paper is the sole responsibility of the authors. Copyright Copyright remains with the authors. Permission to copy for research or teaching purposes is granted on the condition that the authors and the Series are given due acknowledgment. Reproduction in any form for purposes other than research or teaching is forbidden unless prior written permission has been obtained from the authors.

In this paper we propose a temporal extension of Defeasible Logic to model legal modifications, such as abrogation and annulment. Hence, this framework overcomes the difficulty, discussed elsewhere [7], of capturing these modification types using belief and base revision.

We argue that burden of proof (BoP) of the kind present in persuasion does not apply to deliberation. We analyze existing computational models showing that in deliberation agents may answer a critique but there is no violation of the protocol if they choose not to. We propose a norm-governed dialogue where BoP in persuasion is modeled as an obligation to respond, and permissions capture the different types of constraint observed in deliberation.

This paper develops two agent knowledge bases in conceptual graph form, one using the KD45 underlying logical model for belief and one without any underlying logical model for belief. Action-attitudes in the knowledge bases provide contexts that represent the agents' mental attitude towards, and willingness to act upon information in the knowledge bases. Preconditions for communication acts are also represented in the knowledge bases as well as mental attitude changes following communications. Conceptual graphs are a flexible and extendable form of knowledge representation that is used to capture and represent semantic constituents of communications in a form that may be used by software agents. The knowledge base representations in this paper provide software agents a perspective from which they may reason about the communicating agent's beliefs and communication actions.

Agent communication languages such as KQML and the FIPA ACL serve as metalanguages to define software agent message-passing protocols. These metalanguages are incompatible with each other, preventing intercommunication between agents employing different agent communication languages. The primary hindrance to agent intercommunication is the different underlying semantics of the message passing protocols. Conceptual graphs provide a mechanism to bridge this agent communication barrier by representing the semantics of message-passing protocols in the formal representation of conceptual graphs. Semantic content of the KQML tell performative is contrasted with that of the FIPA ACL inform performative and represented in conceptual graphs. The intent is that software agents conversant in CGIF may intelligently translate messages between agents employing different agent communication languages.

In this paper, we describe several interesting design decisions we have taken (with respect to inter-agent messaging) in the reengineered CASA architecture for agent communication and services. CASA is a new architecture designed from the ground up; it is influenced by the major agent architectures such as FIPA, CORBA, and KQML but is intended to be independent (which doesn't imply incompatible). The primary goals are flexibility, extendibility, simplicity, and ease of use. The lessons learned in the earlier implementation have fed the current design of the system. Among the most interesting of the design issues are the use of performatives that form a type lattice, which allows for observers, who do not necessarily understand all the performatives, to nonetheless understand a conversation at an appropriate semantic level. Furthermore, we found it difficult to arrange a portion of the FIPA performatives in a lattice without duplication and complexity. We solved this problem by diverging from FIPA performatives by separating a lot of the performatives into a separate lattice of acts, which work with the performatives, but greatly simplify and enhance the semantic interpretation of the messages. Yet another innovation is the addition of several new fields within a KQML-style message header that allow for further semantic interpretation of the message by an observer who does not necessarily understand the content language. The traditional FIPA fields to, from, sender, and receiver have been extended to include agent (the requester of a service), and actor (the party designated responsible for performing the action specified in the performative/act). These new design considerations add a great deal of flexibility and integrity to an agent communications architecture.

Persuasive negotiation involves negotiating using rhetorical arguments (such as threats, rewards, and appeals), which act as persuasive elements that aim to force or convince an opponent to accept a given proposal. In the case of rewards, these have a positive nature as they use the argument that something positive will happen to the opponent if he accepts to do the requirement sent by the proponent. A proponent agent can generate more than one reward depending on the information he has modeled of his opponent. The problem appears when the agent has to choose a reward, to send to his opponent, among a set of rewards. One measure that could help him in his choice is the strength each reward has. Thus, the goal of this work is to analyze the rewards components and to propose a model for calculating their strength. We propose two ways for calculating the strength of rewards depending on the kind of negotiation the agent is participating. The first proposal is to be used when the agent ...

Applications such as military training simulations, and electronic commerce can benefit from the flexible and responsive nature of multi-agent systems. These applications have inherent timing constraints on the operations and interactions that the agents might perform. This paper presents a real-time agent architecture in which agents communicate, cooperate, coordinate and negotiate to meet the goals of a particular application under specified timing constraints. The architecture provides a real-time CORBA layer to handle underlying real-time communication. It also has a real-time agent communication layer in which agents interact via a real-time extension of a well-known agent communication language.

The manufacturing product life cycle in its conception and designing phases congregates knowledge coming from diverse domains. This knowledge is spread throughout individuals that most of time are not aware of each other vocabulary. In this case opportunities can be lost either because the potential around them is underestimated or correlating themes is burdensome. The work presented here is a tool intended to organize the informal vocabulary used by communities of practice in formal domain categories in order to establish a correlation between them and advice the user of the potential skills net he/she belongs to. Ontologies are used to relate domains and user's profile while agents capture user's preferences and provide useful information. The tool updates general information unburdening the user from tasks she/he is unfamiliar to. Experiments demonstrate the potential of this kind of tool envisaging its broader use and application in other domains.

Em primeiro lugar, gostaria de agradecer ao meu supervisor, o Professor Pedro Henriques, pela supervisão omnipresente e, mais importante ainda, a constante disponibilidade em discutir, analisar e reler resultados, permitindo um desfecho mais rápido e rico em termos de ideias. Ao meu colega, José João, pelas discussões e parcerias donde resultaram ideias inovadoras, algumas delas concretizadas em ferramentas e publicações. Aos meus co-autores, durante os últimos quatro anos, que colaboraram comigo na publicação de vários artigos e outras monografias: Pedro Henriques, José João, Jorge Rocha, Alda Lopes. À Alda Lopes e ao Pedro Sousa o terem aceite fazer as suas teses de mestrado comigo. O seu trabalho deu um empurrão precioso na parte prática desta tese. Aos alunos finalistas que comigo colaboraram na realização de vários projectos reais, dando-me o contacto com a realidade que tão necessário foi para a elaboração de algumas ideias:

This article investigates the intensional programming paradigm for agent communication by introducing context as a first class object in the intensional programming language Lucid. For the language thus extended, a calculus of contexts and a logic of contexts are provided. The paper gives definitions, syntax, and operators for context, and introduces an operational semantics for evaluating expressions in extended Lucid. It is shown that the extended Lucid language, called Agent Intensional Programming Language(AIPL), has the generality and the expressiveness for being an Agent Communication Language(ACL).

The idea of a software entity that performs tasks on behalf of a user across the Internet is now well established. We introduce in this paper a new approach to service discovery and QoS negotiation over the Internet. Our approach presents a framework for service discovery and QoS negotiation at the network level that rely on two concepts: multiagent systems and agent communication languages (ACL). In this framework, a user and service agents engage in a structured communication through the m ediation of a QoS Broker Agent and a Facilitator Agent. Here, the Facilitator Agent acts on behalf of several service agents. It acquires information from these service agents and acts as a single point of contact to supply this information to the User Agent via the QoS Broker Agent. A number of service discovery protocols like the Service Location Protocol (SLP), and Sun Microsystem's Jini has been designed for restricted environments and do not scale to the entire Internet. In order to pro vide an infrastructure for large scale Internet applications, we designed a prototype multi-agent system that is able to discover resources and negotiate QoS at the network level.

Speculative Computation is an effective means for solving problems with incomplete information in an open and distributed environment, such as peer-to-peer environment. It allows such a system to compute tentative (and possibly final) solutions using default knowledge about the current environment, or the agent's perception, even if the communications between peers are delayed or broken. However, previous work in speculative reasoning assumed that agents are hierarchically structured, which may not be the case in reality. We propose a more general multi-agents system with no centralized control. Agents in the framework have equivalent functionalities and can collaborate with each other to achieve their common goals. We characterize the framework using the argumentation semantics of defeasible logic, which provides support of speculative reasoning in the presence of conflicting information. We provide an operational model for the framework and present a prototype implementation of the model.

Agent communication languages such as ACL and KQML provide a standard for agent communication. These languages enable an agent to specify the intention and the content of a message as well as the protocol, the language, and the ontology that are used. For the protocol and the language some standards are available and should be known by the communicating agents. The ontology used in a communication depends on the subject of the communication. Since the number of subjects is almost infinite and since the concepts used for a subject can be described by different ontologies, the development of generally accepted standards will take a long time. This lack of standardization, which hampers communication and collaboration between agents, is known as the interoperability problem. To overcome the interoperability problem, agents must be able to establish a mapping between their ontologies. This paper investigates a new approach to the interoperability problem. The proposed approach requires neither a correspondence between concepts used in the ontologies nor a correspondence between the structure of the ontologies. It only requires that some instances of the subject about which the agents try to communicate are known by both agents.

Agent communication languages such as ACL and KQML provide a standard for agent communication. For the protocol and the language used in the communication, several standards are available. This not the case for the ontology used in the communication. The ontology depends on the subject of the communication. Since the number of subjects is almost infinite and since the concepts used for a subject can be described by different ontologies, the development of generally accepted standards will take a long time. This lack of standardization, which hampers communication and collaboration between agents, is known as the interoperability problem. To overcome the interoperability problem, an approach that enables agents to learn a mapping between their ontologies will be proposed.

Affective characteristics are crucial factors that influence human behavior, and often the prevalence of either emotions or reason varies on each individual. We aim to facilitate the development of agents that simulate humans' reasoning in equilibrium with their affective characteristics. We first identify core processes in an affective BDI agent, and we integrate them into an agent architecture (GenIA 3). These tasks include the extension of the BDI agent reasoning cycle to be compliant with the architecture, and the extension of the agent language (Jason) to support affection-based reasoning, as well as the parametrization of the affectionrationality equilibrium.

Hardware agents as a part of cooperative multi-agent systems act in dynamically changing environments and accomplish tasks jointly. Since the pure hybrid plan representation provides no explicit means to represent particularly communication, task coordination and distribution in the multi-agent system, the proposed plan representation was adjusted to describe these aspects and combines the hybrid approach and an agent communication language. This paper focuses on the plan execution using this plan representation in a developed multi-agent system for robot control. 1 Introduction Hardware agents as a part of cooperative multi-agent systems act in dynamically changing environments and accomplish tasks jointly. This paper focuses on the plan execution using a plan representation in a developed multi-agent system for robot control. The two conventional approaches to the plan representation, the pure reactive and the pure deliberative approaches, have their disadvantages ([7]): the reactive approach ([6]) has no world model and thus lacks the learning capability, the deliberative approach ([8]) is slow and hence unable to solve tasks in a dynamically changing world. The hybrid approach to the planning and the plan execution combines the both conventional approaches making use of their advantages and eliminating disadvantages ([2], [4], [5], [17]). Cooperative multi-agent systems facilitating tasks in dynamically changing environments execute hybrid plans. These plans describe reactive behaviors to commit short-term tasks, allow deliberative planning to execute long-term strategies and show cooperation between agents. Cooperation during plan execution is based on messages in an agent communication language. Our approach is to combine a hybrid plan representation and an agent communication language to execute plans in cooperative multi-agent systems. 2 Plan representation Recent work explores possibilities of a hybrid plan representation in multi-agent systems ([1], [3], [9], [10]). Our work is a contribution in this direction. The proposed approach provides a plan representation for multi-agent systems accomplishing cooperative tasks in the real world (Fig. 1). Hybrid plan representation Agent communication language Proposed approach Fig. 1. Proposed plan representation.

We describe an operational approach to enabling the computational perception required for automated generation of affective behaviour through inter-agent communication in multi-agent real-time environments. The research is investigating the potential of extending current agent communication languages so as they not only convey the content of knowledge exchange but also so they can communicate affective attitudes about the shared knowledge. Providing a necessary component of the framework required for autonomous agent, with affective behaviour, development with which we may bridge the gap between current research in psychological theory and practical implementation of social multi-agent systems.

Current trends in scientific collaboration focus on developing effective Web-based communication tools, such as instant messaging (i.,e IM) or video-conferencing. One objective is to provide informal communication opportunities for collaborating scientists. This paper focuses on developing an assistive technology for predicting where breakdown situations have likely occurred in chat communications. The immediate goal of the assistive technology is to help users cope with discrepancies between their expectations and the tools they are using during scientific collaboration. The ideas in this paper also have far reaching implications, introducing a method that can be used by any human-interactive application to help the application understand when the user does not know what to do. 1 A breakdown situation is a situation in which a conversation "breaks down" due to some influence external from the actual conversation. A technical failure with the communication tool or some other peripheral device is one example.

Intelligent Agents have originated a lot of discussion about what they are, and how they are different from general programs. We describe in this paper a new paradigm for intelligent agents. This paradigm helped us deal with failures in an independent and efficient way. We proposed three types of agents to treat the system in a hierarchical way. A new method to visualize fault tolerant systems (FTS) is proposed, in this paper with the incorporation of intelligent agents, which as they grow and specialized create the Multi-Agent System (MAS). The MAS contains a diversified range of agents, which depending on the perspective will be specialized or will be evolutionary (from our initially proposal they will be specialized for the detection and possible solution of errors that appear in an FTS). The initial structure of the agent is proposed in [1] and it is called a reflected agent with an internal state and in the Method MeCSMA [2].

Abstract: In this paper, we present a multi-agents model for IR, namely IR agents, for information retrieval on WWW. An IR agent consists of three types of agent, Managing agents for extracting the semantics of information and managing the details of co-ordinate agents, Interface ...

E-commerce has become an integral part of everyday life. Many e-commerce systems enable users to browse products, place orders, and track deliveries online. However, these interactions are time-consuming, especially if they do not proceed as expected. Instead of a human user, software can offer automated support to monitor e-commerce transactions to ensure that they are completed by the businesses as planned. Accordingly, this paper studies methods to develop a software agent for monitoring its users' interactions with businesses (PISAGOR). The interactions are represented as commitments, which have been extensively studied in multiagent systems. With a commitment-based specification at hand, the agent knows what the meaning of its interactions are and can therefore reason over its actions. The reasoning is accompanied with the as-good-as relation that compares the agent's current state with its expectations from a transaction. This enables PISAGOR to decide whether the transaction is progressing as expected. Moreover, we propose operational rules for the agent to create expectations based on its commitments and check its progress towards them. We demonstrate via a case study how PISAGOR can detect if a user's interactions are not progressing well and identify a problem for the user to take action.

Different approaches have investigated the syntax and semantic of agent communication. However, all these approaches (including : agent communication languages, conversation policies and dialogue games) have not indicated how agents should dynamically use communications. In fact, most of these approaches have mainly focused on "structure" of dialogues even though developers are more interested in agents' capabilities of having "useful" conversations in respect to their goals rather than in their abilities to structure dialogues. This leads us to propose a theory of use of conversations between agents. This pragmatic theory extends and adapts the cognitive dissonance theory (a major theory of social psychology) to multi-agent systems. In this paper, we show how this theory allows us to provide generic conceptual tools for the automation of both agent communicational behavior and attitude change processes. The cognitive coherence that we propose is formulated in terms of constraints and elements of cognition and allows us to define cognitive incoherences and dialogue utility measures. We show how these measures could be used to solve common problems and answer some critical questions concerning agent communication frameworks use. Finally, the theory is illustrated with an example of dialogue games automatic use.

Although mental states have its own place in the definition of message semantics, social commitments have emerged as a complementing element to circumvent the limitations of using mental state definitions in open multiagent systems. Based on current social commitment approaches, and inspired by theories of language use, we propose a commitmentbased model where messages are defined according to their use as coordinating devices for advancing conversations and the state of social commitments that bring about the actions advancing the joint activities in which agents participate.

Different approaches have investigated the syntax and semantics of agent communication languages. However, these approaches have not indicated how agents should dynamically use communications. Instead of filling this pragmatics gap, most approaches have mainly focused on the ÔstructureÕ of dialogues even though developers are more interested in agentsÕ capabilities of having ÔusefulÕ automated conversations with respect to their goals rather than in their abilities to structure dialogues. This led us to work on a theory of the use of conversations between agents. In this paper, we propose a pragmatics theory which extends and adapts the cognitive dissonance theory (a major theory of social psychology) to multi-agent systems by unifying it with the theory of coherence in thought and action that issues from computational philosophy of mind. Precisely, we show how this theory allows us to provide generic conceptual tools for the automation of both agent communicational behavior and attitude change processes. This new motivational model is formulated in terms of constraints and elements of cognition and allows us to define cognitive incoherences and dialogue utility measures. We show how these measures could be used to solve common problems and answer some critical questions concerning agent communication frameworks use. Finally, our exploration in applying the cognitive coherence pragmatics theory as a new communication layer over classical BDI agents is presented. It relies on our dialogue games based agent communication language (DIAGAL) and our dialogue games simulator toolbox (DGS). The resulting framework provides the necessary theoretical and practical elements for implementing our theory. In doing so, it brings in a general scheme for automatizing agentsÕ communicational behavior as it is exemplified in this article.

Abstract. In recent years, social commitment based approaches have been proposed to solve problems issuing from previous mentalistic based semantics for agent communication languages. This paper follows the same line of thought since it presents a dialogue game based agent communication language (called DIAGAL) which allows agents to manipulate the public layer of social commitments through dialogue, by creating, cancelling,..., updating their social commitments. Then we show how we can study the commitments dynamic to ...

This paper presents a study on how to ensure the coherence of a distributed information system in which information is collected by a multi-agent system with the hypothesis that some agents of the system are dissonant, i.e. can produce or incorrect information.

ISIS, which abbreviates Intelligent Speech for Information Systems, is a trilingual spoken dialog system (SDS) for the financial domain. It handles two dialects of Chinese (Cantonese and Putonghua), as well as English ¨ the predominant languages in our region. The system supports spoken language queries regarding stock market information and simulated personal portfolios. Real-time information is retrieved directly from a dedicated Reuters satellite feed. ISIS provides a system test-bed for our work in multilingual speech recognition and generation, speaker authentication, language understanding and dialog modeling. Furthermore, ISIS supports our initial explorations in: (i) CORBA's interoperability and scalability for SDS development; in conjunction with (ii) asynchronous humancomputer interaction by delegation to KQML software agents.

The notion of agent has of late become popular in the Grid community, as exemplified by several workshops on the use of agents in the Grid. What are agents for the Grid? What is the difference between agents and Web-services? These are questions that we address by describing a port of the SoFAR agent framework to Web services in the context of a bioinformatics Grid. In this first paper, we focus our discussion solely on issues at the transport layer. Through an agent communication language (ACL) and an abstract communication model, we have been able to define a generic API to communications, and are able to support multiple protocols, including the XML protocol, the transport mechanism of Web services. This approach facilitates the development of applications, makes our environment futureproof, and promotes the openness of our Grid architecture to third-party developers.

This paper presents a study on how to ensure the coherence of a distributed information system in which information is collected by a multi-agent system with the hypothesis that some agents of the system are dissonant, i.e. can produce or communicate incorrect information.

In order to perform effective communication, agents must be able to foresee the effects of their utterances on the addressee's mental state. In this paper we study the consequences of an utterance on the mental state of a hearer. Given an agent communication language with a STRIPS-like semantics, we propose a set of criteria that allow the binding of the speaker's mental state to its uttering of a certain sentence. On the basis of these criteria, we give an abductive procedure that the hearer can adopt to partially recognize the speaker's mental state that led to a specific utterance.

This paper describes the Agent-based Imagery and Geospatial processing Architecture (AIGA). AIGA is a novel approach for developing and supporting large-scale querydriven multimedia information systems. AIGA is designed to support collaboration and reuse by de®ning a set of lightweight agents and a combined knowledge encoding and agent communication language called I-XML. Scalability and reuse are achieved by employing a two-tier communication structure. Agents do not communicate directly but rather through a shared page space. We show how this approach simpli®es system design and facilitates collaboration and information sharing among area experts. AIGA is speci®cally designed to allow experts to answer open-ended queries such as`W hat is the current situation at the border between two countries?''. For this environment the reuse of prior strategies reduces the number of computations necessary to construct new answers. We have implemented AIGA in a Java environment. We believe the resulting system demonstrates the eectiveness of our approach in constructing large-scale query-driven multimedia information systems.

This paper presents a study on how to ensure the coherence of a distributed information system in which information is collected by a multi-agent system with the hypothesis that some agents of the system are dissonant, i.e. can produce or communicate incorrect information.

Within the field of odontology, an analysis of the probability of success of endodontic retreatment facilitates the diagnostic and decision-making process of medical personnel. This study presents a case-based reasoning system that predicts the probability of success and failure of retreatments to avoid extraction. Different classifiers were applied during the reuse phase of the case-based reasoning process. The system was tested on a set of patients who received retreatments, and a set of variables considered to be of particular interest, were selected.

The act of delegating a task from one agent to another can be carried out through the performance of one or more imperative communication acts. In this paper, the semantics of such imperatives are specified using a language of actions and states. The logical system that is developed then supports a notion of responsibility. An agent may not only be issued an imperative to directly carry out an event, or achieve some state, but also to be responsible for an event being carried out or state achieved-and these latter commitments might then be serviced through a subsequent act of delegation. The model thus clearly distinguishes between different classes of responsibility and different forms of delegation, and it is shown how this sound theoretical foundation can then be applied in specifying the semantics of imperatives in agent communication languages. 1. the distinction between the delegation of actions to be performed and states of affairs to be achieved; and 2. the restrictions on the further delegation of the activity concerned (i.e. whether further delegation is permitted, forbidden or required. There are, of course, many more issues that must be considered in the development of a complete theory of delegation; for example, the discussion is restricted to individuals rather than groups of agents [19, 23]. However, considering these two issues alone does mean that a number of distinct situations must be considered: (a) "I don't care who achieves (state of affairs) ¤ , but it must be achieved." (b) "I don't care who does (action) ¥ , but it must be done." (c) "You must, through your own, direct, intervention achieve ¤ ." (d) "You must, through your own, direct, intervention do ¥. " (e) "You must ensure that ¤ is achieved by someone other than yourself." (f) "You must ensure that ¥ is done by someone other than yourself." Possibly the most common mechanism employed in the delegation of activity (especially in multi-agent systems) is through direct communication. Knowledge level [22] communication between agents through speech act based [2, 28] agent communication languages (ACLs) is both an active area of research [31, 26] and of standardisation [11, 10]. These languages typically include indicatives (or assertions) such as 'tell' (KQML) and 'inform' (FIPA); for example, "It's raining". Queries or questions are also common (i.e. interrogatives) such as 'ask-if' (KQML) and 'query-if' (FIPA); for example, "Is it raining?". In addition to these, imperatives are used to issue commands, give advice or request action; for example, "bring the umbrella". Examples of imperative message types in ACLs are 'achieve' (KQML) and 'request' (FIPA). An intuitive explanation of these message types is that the sender is attempting to influence the recipient to act in some way. In fact, an attempt to influence the mental state of the hearer (or recipient of a message) is common to all knowledge level communication. For example, an agent utters an indicative such as "It's raining" with the intention of inducing a belief by means of the recognition of this intention [12]. In other words, the speaker is attempting to influence the hearer to adopt a belief about the weather. Similarly, the imperative "bring the umbrella" is an attempt to influence the hearer's future actions by means of the hearer recognising that this is the intention of the speaker. Following Searle's [28] description of the types of illocutionary (or communicative) act, Cohen and Levesque [8] provide a model in which such acts are construed as attempts by the speaker to change the mental state of the hearer. For example, a request for the hearer to do some action, ¥ , is an attempt to change the hearer's mental state in such a way that it becomes an intention of the hearer to do ¥. The hearer, being an autonomous agent, may refuse. This is, of course, different from misunderstanding the speaker. With this in mind, Cohen and Levesque [8] distinguish between a speaker's goal of performing an act, and the speaker's intention behind the act. The goal, in the case of an imperative, is that the hearer believes that the speaker intends the hearer to act and the hearer acts accordingly. The intention, by contrast, is only that the hearer believes that the speaker had that communicative goal. If the intention of the speaker is not understood by the hearer, then the communicative act is unsuccessful. A communicative act

The act of delegating a task by one agent to another can be carried out by the performance of one or more communicative acts. Such acts may not only be directed to another individual, but also to a group of agents. In this paper, the semantics of imperatives are explored with reference to extant logics of agentative action, and in the context of the referent of an imperative being either an action or a state of affairs. The particular case of issuing of an imperative to a group of individuals is then discussed from both theoretical and practical perspectives, and the importance of distinguishing between groups with differing characteristics emphasised by analysis of an extended real-world example.

A temporal dimension must be present in interactions between agents that must cooperate in continuously changing environments. In this paper, we present the definition of a temporeJ agent communication language. This language uses a sophisticated communication model based on the speech act theory. It is the component of a more important research dealing with the study of temporal reasoning in multi-agent systems. This work takes place, also, in the building of an interaction toolbox with temporal abilities in the context of a Multi-Agent System Platform in construction in our laboratory.

is one of six departments that make up the School of Business at the University of Otago. The department offers courses of study leading to a major in Information Science within the BCom, BA and BSc degrees. In addition to undergraduate teaching, the department is also strongly involved in postgraduate research programmes leading to MCom, MA, MSc and PhD degrees. Research projects in spatial information processing, connectionist-based information systems, software engineering and software development, information engineering and database, software metrics, distributed information systems, multimedia information systems and information systems security are particularly well supported. The views expressed in this paper are not necessarily those of the department as a whole. The accuracy of the information presented in this paper is the sole responsibility of the authors. Copyright Copyright remains with the authors. Permission to copy for research or teaching purposes is granted on the condition that the authors and the Series are given due acknowledgment. Reproduction in any form for purposes other than research or teaching is forbidden unless prior written permission has been obtained from the authors.

is one of seven departments that make up the School of Business at the University of Otago. The department offers courses of study leading to a major in Information Science within the BCom, BA and BSc degrees. In addition to undergraduate teaching, the department is also strongly involved in postgraduate research programmes leading to MCom, MA, MSc and PhD degrees. Research projects in spatial information processing, connectionist-based information systems, software engineering and software development, information engineering and database, software metrics, distributed information systems, multimedia information systems and information systems security are particularly well supported. The views expressed in this paper are not necessarily those of the department as a whole. The accuracy of the information presented in this paper is the sole responsibility of the authors. Copyright Copyright remains with the authors. Permission to copy for research or teaching purposes is granted on the condition that the authors and the Series are given due acknowledgment. Reproduction in any form for purposes other than research or teaching is forbidden unless prior written permission has been obtained from the authors.

is one of six departments that make up the Division of Commerce at the University of Otago. The department offers courses of study leading to a major in Information Science within the BCom, BA and BSc degrees. In addition to undergraduate teaching, the department is also strongly involved in postgraduate research programmes leading to MCom, MA, MSc and PhD degrees. Research projects in spatial information processing, connectionist-based information systems, software engineering and software development, information engineering and database, software metrics, distributed information systems, multimedia information systems and information systems security are particularly well supported.

In this paper we propose reducing the degree of human interpretation currently necessary to understand an interaction protocol by describing at an abstract level the required agent actions that must be 'plugged into' the protocol for it to be executed. In particular, this can be done by designing and publishing ontologies describing the input and output data that are processed during the protocol's execution together with the actions and decisions that the agents must perform. An agent (or agent developer) that has previously defined mappings between the internal agent code and the actions and decisions in an ontology would then be able to interpret any interaction protocol that is defined with reference to that ontology. The discussion is based on the use of Coloured Petri Nets to represent interaction protocols and the Unified Modeling Language for ontology modelling.

This paper describes a multi-agent platform to be used for the integration of environmental information that may be distributed over a network. The system is designed to work as a collection of collaborating agents. Information sources are encapsulated as data source agents that accept messages in an agent communication language. Here we describe how queries can be entered into the system and information collected from multiple sources. A key component of the query module is the planner agent, which takes a query and transforms it first to a calculus, then to an algebraic expression in order to break it into subqueries which an executor agent can send to the data source agents. As part of this process, the query is translated from user level ontologies to lower level ontologies relevant to the data source agents. Query results need not be returned within an ACL message, but may instead be represented by a CORBA object reference which may be used to obtain the result set. The architecture and operation of these agent components is described and an example is presented of how environmental information can be queried.

Abstract: In this paper, we present a multi-agents model for IR, namely IR agents, for information retrieval on WWW. An IR agent consists of three types of agent, Managing agents for extracting the semantics of information and managing the details of co-ordinate agents, Interface ...

This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we present the theory of signalling acts. In contrast to current approaches to communication, this account is neither intention-based nor commitment-based, but convention-based. Next, we explore ways of embedding that theory within an account of conversation. We move here from an account of the basic types of communicative act (the statics of communication) to an account of their role in sequences of exchanges in communicative interaction (the dynamics of communication). Finally, we apply the framework to the analysis of conversational protocols such as the English auction protocol. We propose to give a compact expression of conversation protocols by means of a formula of the object-language. We also use this kind of representation to provide the basis for a procedure for keeping a record of the conventional effects achieved in a conversation. A corresponding axiomatic presentation is given, and shown to be sound and complete with respect to our proposed semantics.