Mechanisms for Automated Negotiation in State Oriented Domains

This paper lays part of the groundwork for a domain theory of negotiation, that is, a way of classifying interactions so that it is clear, given a domain, which negotiation mechanisms and strategies are appropriate. We define State Oriented Domains, a general category of interaction. Necessary and sufficient conditions for cooperation are outlined. We use the notion of worth in an altered definition of utility, thus enabling agreements in a wider class of joint-goal reachable situations. An approach is offered for conflict resolution, and it is shown that even in a conflict situation, partial cooperative steps can be taken by interacting agents (that is, agents in fundamental conflict might still agree to cooperate up to a certain point). A Unified Negotiation Protocol (UNP) is developed that can be used in all types of encounters. It is shown that in certain borderline cooperative situations, a partial cooperative agreement (i.e., one that does not achieve all agents' goals) might be preferred by all agents, even though there exists a rational agreement that would achieve all their goals. Finally, we analyze cases where agents have incomplete information on the goals and worth of other agents. First we consider the case where agents' goals are private information, and we analyze what goal declaration strategies the agents might adopt to increase their utility. Then, we consider the situation where the agents' goals (and therefore stand-alone costs) are common knowledge, but the worth they attach to their goals is private information. We introduce two mechanisms, one 'strict', the other 'tolerant', and analyze their affects on the stability and efficiency of negotiation outcomes.Comment: See http://www.jair.org/ for any accompanying file

On the relation of classical and temporal planning

Abstract This paper explores a research strategy for a uniform and rational reconstruction of AI planning techniques. The strategy relies on two assumptions: (1) classical planners like STRIPS or SNLP are restricted variants of temporal planners like DEVISER, and (2) temporal planners may be best constructed atop a time map manager (TMM). The strategy aims at a reconstruction of timeless, classical as well as temporal systems in a TMM-based architectural framework. However, this paper shows that assumed restricted variants of DEVISER cannot be adequately recast in the TMM framework: this result is shown to hold for classical nonlinear planners like SNLP, and one reasonable extension by possibly simultaneous actions. Hence, in accordance with recent complexity results, this paper calls the intutively appealing research strategy into question. Motivation Classical planning in the tradition of STRIPS DEVISER The rational reconstruction of planners described in the literature is an important objective of current research. Chapman We are interested in planners which may be located in the middle-ground between classical nonlinear planners like NOAH When pursuing the research strategy assuming that any point in the spectrum is a restricted variant of DEViSER-style systems, and that general temporal planners may be adequately constructed on top of a TMM, two unexpected problems arise: equivalent recasting of neither (1) classical nonlinear planners nor (2) reasonable extension by simultaneous actions is possible within the TMM framework, when keeping the idea of clearly separating temporal reasoning and plan construction. These problems are caused by the facts that (1) conflict-free time map does not neccessarily represent a correct nonlinear plan, and (2) there is (at least) one sonable but not recastable alternative to TMM's built-in criterion for simultaneous exeeutability of actions. The paper has the following structure: After introducing basic definitions in section 2, two reasonable approaches to extending the planning framework by simultaneous actions are described in section 3. The TMMbased construction of the temporal, nonlinear planner 1 Recent complexity considerations 4

Agent interaction: abstract approaches to modelling, programming and verifying multi-agent systems

Computer systems and their applications are becoming increasingly more complicated. Modern systems often consist of multiple independent parts (hardware and software), which interact with their environment. Computers communicate with other computers, exchange information with and receive commands from their human users and receive information about their physicalor virtual environment. This high degree of interactivity leadsto an inherently larger degree of complexity, which needs to be managed and controlled. An important means to reduce complexity is abstraction. Abstraction meansfinding intuitive concepts to model the complex reality and leaving outunderlying details. In the field of multi-agent systems, in which the work ofthis thesis fits, anthropomorphic abstractions are oftenused. Anagent is an autonomous piece of software, designed and/or built in terms ofanthropomorphic concepts, which interacts with other agents and its environmentin such a way that it takes into account the dynamic circumstances and strives to achieve its aims. In this thesis, we focus on agent interaction. Starting from different viewpoints in the field ofmulti-agent systems, we introduce a number of new abstract concepts for agentinteraction. A danger of using abstraction is that abstract concepts areintroduced without grounding them in the computational reality. Therefore, wetake care to always relate our abstract notions to lower-level concepts. We start in Chapter 2 by anchoring three already existing and popular agentconcepts, which are belief, desire and intention, in externally observableagent behaviour. We provide criteria which formally describe when behaviour of an agent indicates that the agent has a certainmental state (a belief, desire or intention). These criteria can be used by agents themselves to attribute belief, desire and intention to other agents, onthe basis of observed behaviour. Chapter 3 deals with agent verification. As the complexity of agent systems ishigh, verification of these systems is very difficult. We develop two principleswhich aid in making verification of agent systems more manageable. The firstprinciple is language abstraction. We use two logical languages to phraseproperties, an abstract one and a detailed one. Properties in theabstract language are shorter and more intuitive than properties in thedetailed language. The second principle is constructing abstract, generic,reusable systems of properties and proofs. In Chapter 4 we present a new model of agents, which focuses on agentinteraction. Our model explicitly includes the dynamic environment. We have areal-time model: actions have a duration. This means that actions of one or more agents can takeplace during overlapping time frames, leading to harmful interference orbeneficial synergy. Agents can perform group actions, which means that themembers of the group perform individual actions in a coordinated manner. In Chapter 5, we develop the programming language GrAPL (Group AgentProgramming Language), intended to program multi-agent systems in which agentscan form temporary alliances to perform group actions. Before a group actions isperformed, the agents communicate with each other to pose demands on details ofthe action and the composition of the group of actors. The programming languagehas a formal operational semantics. We generalise the idea of Chapter 5 in Chapter 6, by looking at group plansinstead of group actions. A group plan is a composed action, consisting of bothindividual actions and group actions, which are partially ordered in time. Weprovide a new high-level coordination language which heterogeneous agents canuse to discuss group plans and to execute them in a synchronised manner