Showing papers on "Contract Net Protocol published in 2002"

Sold!: auction methods for multirobot coordination

Abstract: The key to utilizing the potential of multirobot systems is cooperation. How can we achieve cooperation in systems composed of failure-prone autonomous robots operating in noisy, dynamic environments? We present a method of dynamic task allocation for groups of such robots. We implemented and tested an auction-based task allocation system which we call MURDOCH, built upon a principled, resource centric, publish/subscribe communication model. A variant of the Contract Net Protocol, MURDOCH produces a distributed approximation to a global optimum of resource usage. We validated MURDOCH in two very different domains: a tightly coupled multirobot physical manipulation task and a loosely coupled multirobot experiment in long-term autonomy. The primary contribution of the paper is to show empirically that distributed negotiation mechanisms such as MURDOCH are viable and effective for coordinating physical multirobot systems.

Animated specifications of computational societies

Abstract: E-markets and negotiation protocols are two types of application domains that can be viewed as open computational societies. Key characteristics of such societies are agent heterogeneity, conflicting individual goals and limited trust. The risk that members of such societies will not conform to specifications imposes the need for a framework that will facilitate the designers to determine to what extent it is desirable to deploy their agents in such societies. We address this need by presenting a formal framework for specifying, animating, and ultimately reasoning about and verifying the properties of open computational systems. We view computational systems from an external perspective, aiming to account for the institutional and social aspects of these systems. We identify the key concepts and illustrate how they are used by formalising an example employing the contract net protocol. The framework and associated logical inferences have been implemented as a software platform that provides automated animation of the global states of an open system (society) during its execution. Simulations have demonstrated that the implementation of the framework establishes a foundation for a rich, formal representation of open computational societies.

The eager bidder problem: a fundamental problem of DAI and selected solutions

Abstract: The contract net protocol is a widely used protocol in DAI, as it proved to be a flexible and low communication interaction protocol for task assignment. It is however not clear in which manner agents participating in a contract net should allocate their resources if a large number of contract net protocols is performed concurrently. If the agent allocates too many resources too early, e.g. when making a bid, it may not get any bid accepted and resources have been allocated while other negotiations have come to an end and it is no longer able to make bids for them. If it allocates resources too late, e.g. after being awarded the contract, it may have made bids for more tasks than its resources allow for, possibly all being accepted and resulting in commitments that cannot be kept. We call this dilemma the Eager Bidder Problem. Apart from resource allocation this problem is of further importance as it constitutes the "dual" problem to engaging in multiple simultaneous first-price sealed-bid auctions.We present an ad hoc solution and two more complex strategies for solving this problem. Furthermore, we introduce a new method based on a statistical approach. We describe these mechanisms and how they deal with the concept of commitment at different levels. We conclude with criteria for the decision which of these mechanisms is best selected for a given problem domain.

To Commit or Not to Commit: Modeling Agent Conversations for Action

Abstract: Conversations are sequences of messages exchanged among interacting agents. For conversations to be meaningful, agents ought to follow commonly known specifications limiting the types of messages that can be exchanged at any point in the conversation. These specifications are usually implemented using conversation policies (which are rules of inference) or conversation protocols (which are predefined conversation templates). In this article we present a semantic model for specifying conversations using conversation policies. This model is based on the principles that the negotiation and uptake of shared social commitments entail the adoption of obligations to action, which indicate the actions that agents have agreed to perform. In the same way, obligations are retracted based on the negotiation to discharge their corresponding shared social commitments. Based on these principles, conversations are specified as interaction specifications that model the ideal sequencing of agent participations negotiating the execution of actions in a joint activity. These specifications not only specify the adoption and discharge of shared commitments and obligations during an activity, but also indicate the commitments and obligations that are required (as preconditions) or that outlive a joint activity (as postconditions). We model the Contract Net Protocol as an example of the specification of conversations in a joint activity.

Comparison of Multiple Agent-Based Organizations for Satellite Constellations

Abstract: A comparison is made of several autonomous software architectures for multiple satellite systems. Multiple, agent-based satellite systems are envisioned because they are capable of higher performance, lower cost, better fault tolerance, recone gurability, and upgradability. Software agents are dee ned at the spacecraft and functional levels, using a wide variety of algorithms including multivariable control, linear programming, fuzzy logic, contract net protocol, negotiation, and radar placement. The agent dee nitions allow many types of agent-based software architectures to be developed. Several novel agent-based architectures with a more traditional system for a distributed space-based radar mission are compared. Agent-based simulations of several mission scenarios show the autonomous operation of different organizations of increasing autonomy and compare the benee ts and drawbacks of each.

Scalability Analysis of the Contract Net Protocol

Abstract: Multi-agent systems have been proposed for creating large grid computing systems. This paper investigates the performance and scalability of the Contract Net protocol. We have developed a testbed multi-agent system and measured the task execution times under different agent load. The paper shows how the system response time depends on the number of agents and the deadline value.

To commit or not to commit: modelling agent conversations for action

Abstract: Conversations are sequences of messages exchanged among interacting agents. For conversations to be meaningful, agents ought to follow commonly known specifications limiting the types of messages that can be exchanged at any point in the conversation. These specifications are usually implemented using conversation policies (which are rules of inference) or conversation protocols (which are predefined conversation templates). In this article we present a semantic model for specifying conversations using conversation policies. This model is based on the principles that the negotiation and uptake of shared social commitments entail the adoption of obligations to action, which indicate the actions that agents have agreed to perform. In the same way, obligations are retracted based on the negotiation to discharge their corresponding shared social commitments. Based on these principles, conversations are specified as interaction specifications that model the ideal sequencing of agent participations negotiating the execution of actions in a joint activity. These specifications not only specify the adoption and discharge of shared commitments and obligations during an activity, but also indicate the commitments and obligations that are required (as preconditions) or that outlive a joint activity (as post-conditions). We model the Contract Net Protocol as an example of the specification of conversations in a joint activity.

P2P M-commerce in pervasive environments

Abstract: Pervasive environments are characterized by the presence of wireless devices ranging from sensors to mobile PDA-phones to laptops. Peer-to-Peer (P2P) information sharing in such environments presents a tremendous opportunity for people and devices to exchange information such as music, pictures, documents and stock tickers with peers. Information that has a monetary value introduces a whole new set of problems for P2P interaction in pervasive environments. In this work, we present the design of a middleware that attempts to solve these problems using concepts of the Contract Net Protocol, Semantic Service Discovery and secure transaction protocols.

Modeling and control of holonic manufacturing systems based on extended contract net protocol

Abstract: This paper focuses on conflict resolution and control in the context of holonic manufacturing systems based on cooperative agents. Holonic manufacturing systems requires a robust mechanism to dynamically allocate the available resources to achieve the production goal. Conflicts among agents usually occur when multi-agent framework is applied to control manufacturing systems. Conflicts take place if more than two agents requesting the same resources to carry out their actions. An effective conflict resolution mechanism to dynamically and robustly allocate available resources to achieve the goal of production is the key to optimization of performance and resource utilization. In this paper, a framework is proposed to adaptively synthesize Petri Nets to control holonic manufacturing systems based on the contract net protocol to resolve conflicts and Petri Nets to model the system and test feasibility of commitment.

Stigmergy in holonic manufacturing systems

Abstract: Multi-agent coordination and control, as encountered in holonic manufacturing system implementations, can be classified according to two categories of agent interaction schemes. In the first category, agents explicitly interact and negotiate with each other. A well-known example is the contract net protocol. In the second category, the agents interact and coordinate indirectly by changing their "environment". These changes are observed by other agents and influence their behaviour. A form of coordination based on such an indirect interaction is called stigmergy. This paper describes a specific type of coordination and control belonging to the second category. It also discusses how this enables the design of a system in which agents make global information locally available to other agents without any agent becoming exposed to global system properties.

Communication Mechanism in a Distributed System of Mobile Robots

Abstract: This paper addresses problems of communication and information sharing in the system of heterogenous mobile robots and stationary sensors. We analyze information sharing between robots and sensors treated as agents, and propose a framework based on the Contract Net Protocol. We define the software architecture for the communication system. This architecture, based on an object-oriented library, provides agents with unified communication interfaces.

Modelling agent conversations for action

Abstract: Conversations are sequences of messages exchanged between interacting software agents. For conversations to be meaningful, agents ought to follow conversational principles governing the exchange of messages at any point in a conversation. These principles must be defined in publicly verifiable terms (if they are to be used in open environments) and must allow the composition of flexible conversations (if they are to account for the context in which they occur). The main contribution of this thesis is to define a unified model for conversations for action that fulfills these requirements. The conversational principle in this model is the negotiation of shared social commitments, which entails the adoption and discard of obligations to act. This principle is encoded using conversation policies, which govern the form of conversations according to the observable state of interacting agents. The applicability of this model is illustrated through the modelling of two example conversations: one on the Contract Net Protocol, and the second on an electronic bookstore scenario.

Multi-Agent-Systems and Applications II 9th ECCAI-ACAI/EASSS 2001, AEMAS 2001, HoloMAS 2001. Selected Revised Papers

Abstract: Multi-Agent Systems and Applications ACAI 2001: Selected Tutorial Papers.- Intelligent Agents: The Key Concepts.- Motivated Agent Behaviour and Requirements Applied to Virtual Emergencies.- Software Agents for Electronic Business: Opportunities and Challenges.- From Simulated Dialogues to Interactive Performances.- Cooperating Agents for Holonic Manufacturing.- Multi-Agent Systems and Applications ACAI 2001: Selected Student Papers.- Self-Stabilizing Distributed Algorithms for Defeat Status Computation in Argumentation.- Replanning in a Resource-Based Framework.- Distributed Branch and Bound Algorithm in Coalition Planning.- Formal Conversations for the Contract Net Protocol.- Adaptive Agents in Argumentation-Based Negotiation.- Flexible Load Balancing in Distributed Information Agent Systems.- Autonomous Agents Applied to Manufacturing Scheduling Problems: A Negotiation-Based Heuristic Approach.- Adaptability and Embodiment Using Multi-Agent Systems AEMAS 2001: Selected Papers.- Adaptability and Embodiment Using Multi-Agent Systems.- Distributed Shared Agent Representations.- Modeling Adaptive Multi-Agent Systems Inspired by Developmental Biology.- Industrial Applications of Holonic and Multi-Agent Systems HoloMAS 2001: Selected Papers.- Holons & Agents: Recent Developments and Mutual Impacts.- Material Handling Problem: FIPA Compliant Agent Implementation.- Industrial MAS for Planning and Control.- An Integral Implementation of a Machine-Holon Applying the ZEUS Agent Framework.- ExPlanTech: Exploitation of Agent-Based Technology in Production Planning.- A Holonic Approach to Reconfiguring Real-Time Distributed Control Systems.- Rationales for Holonic Applications in Chemical Process Industries.- Distributed Deadline Control in Holonic Manufacturing Systems.- CPlanT: Coalition Planning Multi-Agent System for Humanitarian Relief Operations.

Adaptive Fault Tolerant Hospital Resource Scheduling

Abstract: In a distributed hospital system, different hospitals should collaborate among themselves for sharing their resources to provide better and faster service to the patients. We address the distributed hospital resource scheduling problem and apply the Generalized Partial Global Planning (GPGP) approach used for multiagent systems for the same. An adaptive coordination mechanism based on the contract net protocol is proposed to support inter-hospital collaboration. We have performed simulation studies and the experimental results show that our coordination mechanism performs better than commonly used schemes. Fault handling mechanisms are presented so that the system continues to provide service even in the presence of faults. The proposed approach is applicable in contexts other than the distributed hospital system as well.

Formal Conversations for the Contract Net Protocol

Abstract: In this paper we present a fairly complex example of how the social model for agent conversations based on social commitments we have developed in the past formally supports the implementation of conversations for the Contract Net Protocol.

Real time issues on coordinating cooperative autonomous objects

Abstract: Next-generation real-time distributed systems present increasing demands for flexibility and adaption from computing objects, due to dynamic requirements and complexity. To meet those demands for flexibility and adaptation and at the same time ensure a predictable temporal behavior is a challenge that the great majority of existing methods can not cope with. Key properties like optimization of global utility fairness and timeliness must be taken in account, specially at the communication and coordination levels. In this paper, preliminary results of an ongoing research project which aims to provide a framework for developing real-time distributed applications using the concept of real-time agents are presented. The approach focuses on aspects such as agent communication and coordination schemes. It combines known results from distributed agent systems, such as the contract net protocol for selecting the most suitable agent for a solving a given problem, with real-time message and task scheduling algorithms. In order to illustrate the concepts proposed, a robotic system is presented as a case-study.

Agent Coordination Mechanisms for Scheduling System Based MAS

Abstract: To overcome CNP's (Contract Net Protocol) defects in Shop-Floor Scheduling System based MAS, a new method was presented dealing with task distributing and scheduling based on GPGP (Generalized Partial Global Planning) coordination mechanisms, and TAEMS (Task Analysis, Environment Modeling and Simulation language). A task/capability environment model and the process of scheduling part were put forward that can provide the basic structure of knowledge-based scheduling. In MM-MES, a manufacturing execution system based MAS, they were implemented to research distributed manufacturing system's scheduling and coordination.

Dynamic Social Knowledge: The Timing Evidence

Abstract: A comparative evaluation among the Contract Net Protocol, the Coalition Based on Dependence* and the Dynamic Social Knowledge cooperation strategies is presented in this paper. This evaluation uses the experimental results from a soft real-time application extracted from the robot soccer problem and focuses on the cooperation convergence time and on the amount of exchanged messages. Also one new concept called Plan Set is presented in this paper.

Specification and analysis of the contract net protocol based on state machine model

Abstract: In this paper, we clarify the properties of the contract net protocol based on its formal specification. To specify the contract net protocol, we propose a formal specification method for an agent system. In this method, agents are modeled as communicating finite state machines. To deal with the behavior of agents and its time passage explicitly, we incorporate the concept of time into the communicating finite state machine. The contract net protocol is specified based on the specification method proposed in this paper. From the specification, we analyze the possibility about agent deadlock and its avoidance solution. key words: multi-agent system, contract net protocol, formal

Research of Agent communication model and Agent's negotiation protocol in Multi-Agent based manufacturing system

Abstract: Based on analysis of the characteristics of agent communication in Multi-Agent Systemapplied in manufacturing system, this paper proposes an agent cooperation process basedon Contract Net Protocol and a solution for negotiation conflict avoidance, designs anagent communication Model, using KQML as communication language and CORBAstandard as the base of agent's communication and interoperation, and lastly, analysesthis type of agent communication mode via an application of MAS in job shop scheduling.

An Analysis on Game Theoretic Negotiation Dynamism Based on Multi-Agent Paradigm in Virtual Enterprise

Abstract: In this paper, we focus on negotiation process in VE formulation as a basic research to clarify its effective management. Each enterprise in VE is defined as agent in multi-utilities and a framework of multi-agent programming with game theoretic approach is newly proposed as negotiation algorithm amongst the agents. Each unit is defined as agent in our VE model, and their decision makings are formulated as a gaine theoretic methodology. We adopt CNP (Contract Net Protocol) as the coordination and negotiation mechanism amongst the units. CNP models transfer of control in a distributed system with the metaphor of negotiation among autonomous intelligent beings. CNP consists of a set of nodes that negotiate with one another through a set of message. Nodes generally represent the distributed computing resources to be managed, correspond to “enterprises” in this paper. We develop a computer simulation model to forni VE through multiple negotiations amongst several potential members in the negotiation domain, and finally clarify the formulation dynamism with the negotiation process.