Agent Theories, Architectures, and Languages: A Survey <s> Cohen & Levesque -intention <s> This thesis describes a theoretical framework for modelling cooperative dialogue. The linguistic theory is a version of speech act theory adopted from Cohen and Levesque, in which dialogue utterances are generated and interpreted pragmatically in the context of a theory of rational interaction. The latter is expressed as explicitly and formally represented principles of rational agenthood and cooperative interaction. The focus is the development of strategic principles of multi-agent interaction as such a basis for cooperative dialogue. In contrast to the majority of existing work, these acknowledge the Positive role of conflict to multi-agent cooperation. and make no assumptions regarding the benevolence and sincerity of agents. The result is a framework wherein agents can resolve conflicts by negotiation. It is a preliminary stage to the future building of computer models of cooperative dialogue for both HCI and DAI, which will therefore be more widely and generally applicable than those currently in existence. ::: ::: The theory of conflict and cooperation is expressed in the different patterns of mental states which characterise multi-agent conflict, cooperation and indifference as three alternative postural relations. Agents can recognise and potentially create these. Dialogue actions are the strategic tools with which mental states can be manipulated, whilst acknowledging that agents are autonomous over their mental states; they have control over what they acquire and reveal in dialogue. Strategic principles of belief and goal adoption are described in terms of the relationships between autonomous agents' beliefs, goals, preferences, and interests, and the relation of these to action. Veracity, mendacity, concealing and revealing are defined as properties of acts. The role of all these elements in reasoning about dialogue action and conflict resolution, is tester in analyses of two example dialogues; a record of a real trade union negotiation and an extract from "Othello" by Shakespeare. <s> BIB001 </s> Agent Theories, Architectures, and Languages: A Survey <s> Cohen & Levesque -intention <s> This paper provides a logical analysis of the concept of intention as composed of two more basic concepts, choice (or goal) and commitment. By making explicit the conditions under which an agent can drop her goals, i.e., by specifying how the agent is committed to her goals, the formalism provides analyses for Bratman's three characteristic functional roles played by intentions [Bratman, 1986], and shows how agents can avoid intending all the foreseen side-effects of what they actually intend. Finally, the analysis shows how intentions can be adopted relative to a background of relevant beliefs and other intentions or goals. By relativizing one agent's intentions in terms of beliefs about another agent's intentions (or beliefs), we derive a preliminary account of interpersonal commitments. <s> BIB002 </s> Agent Theories, Architectures, and Languages: A Survey <s> Cohen & Levesque -intention <s> Joint action by a team does not consist merely of simultaneous and coordinated individual actions; to act together, a team must be aware of and care about the status of the group effort as a whole. We present a formal definition of what it could mean for a group to jointly commit to a common goal, and explore how these joint commitments relate to the individual commitments of the team members. We then consider the case of joint intention, where the goal in question involves the team performing some action. In both cases, the theory is formulated in a logical language of belief, action, and time previously used to characterize individual commitment and intention. An important consequence of the theory is the types of communication among the team members that it predicts will often be necessary. <s> BIB003 </s> Agent Theories, Architectures, and Languages: A Survey <s> Cohen & Levesque -intention <s> Abstract : This paper derives the basis of a theory of communication from a formal theory of rational interaction. The major result is a demonstration that illocutionary acts need neither be primitive, nor explicitly recognized. As a test case, we derive Searle's conditions on requesting from principles of rationality coupled with a theory of imperatives. The theory rests on a formal account of intention and distinguishes insincere or nonserious imperatives from true requests. A theory of purposeful communication thus emerges as a consequence of principles of action and interaction. <s> BIB004
Probably the best-known and most influential contribution to the area of agent theory is due to Cohen and Levesque BIB002 . Their formalism was originally used to develop a theory of intention (as in 'I intend to…'), which the authors required as a pre-requisite for a theory of speech acts BIB004 . However, the logic has subsequently proved to be so useful for reasoning about agents that it has been used in an analysis of conflict and cooperation in multi-agent dialogue BIB001  , as well as several studies in the theoretical foundations of cooperative problem solving BIB003    . Here, we shall review its use in developing a theory of intention. When building intelligent agents -particularly agents that must interact with humans -it is important that a rational balance is achieved between the beliefs and goals of the agents: 'For example, the following are desirable properties of intention: An autonomous agent should act on its intentions, not in spite of them; adopt intentions it believes are feasible and forgo those believed to be infeasible; keep (or commit to) intentions, but not forever; discharge those intentions believed to have been satisfied; alter intentions when relevant beliefs change; and adopt subsidiary intentions during plan formation'. [28, p214] Following Bratman,   , Cohen and Levesque identify seven properties that must be satisfied by a reasonable theory of intention: 1. Intentions pose problems for agents, who need to determine ways of achieving them. 2. Intentions provide a 'filter' for adopting other intentions, which must not conflict. 5. Agents do not believe they will not bring about their intentions. 6. Under certain circumstances, agents believe they will bring about their intentions. 7. Agents need not intend all the expected side effects of their intentions. Given these criteria, Cohen and Levesque adopt a two-tiered approach to the problem of formalizing a theory of intention. First, they construct a logic of rational agency, 'being careful to sort out the relationships among the basic modal operators' [28, p221] . On top of this framework, they introduce a number of derived constructs, which constitute a 'partial theory of rational action' [28, p221] ; intention is one of these constructs. Syntactically, the logic is a many-sorted, quantified, multi-modal logic with equality, containing four primary modalities: (BEL x ϕ) Agent x believes ϕ (GOAL x ϕ) Agent x has goal of ϕ (HAPPENS α) Action α will happen next (DONE α) Action α has just happened The that an agent will not have a goal of something it believes will not happen. Worlds in the formalism are a discrete sequence of events, stretching infinitely into past and future. The two basic temporal operators, HAPPENS and DONE, are augmented by some operators for describing the structure of event sequences, in the style of dynamic logic  . The two most important of these constructors are ';' and '? ': α; α′ denotes α followed by α′ α? denotes a 'test action' α The standard future time operators of temporal logic, ' ' (always), and '}' (sometime) can be defined as abbreviations, along with a 'strict' sometime operator, LATER: A temporal precedence operator, (BEFORE p q) can also be derived, and holds if p holds before q. An important assumption is that all goals are eventually dropped: }¬(GOAL x (LATER p)). The first major derived construct is a persistent goal. So, an agent has a persistent goal of p if: 1. It has a goal that p eventually becomes true, and believes that p is not currently true. 2. Before it drops the goal, one of the following conditions must hold: (i) the agent believes the goal has been satisfied; or (ii) the agent believes the goal will never be satisfied. It is a small step from persistent goals to a first definition of intention, as in 'intending to act'. Note that 'intending that something becomes true' is similar, but requires a slightly different definition; see BIB002 . Cohen and Levesque go on to show how such a definition meets many of Bratman's criteria for a theory of intention (outlined above). A critique of Cohen and Levesque's theory of intention may be found in  ; space restrictions prevent a discussion here.