Branching-time temporal logics have proved to be an extraordinarily successful tool in the formal specification and verification of distributed systems. Much of their success stems from the tractability of the model checking problem for the branching time logic ctl, which has made it possible to implement tools that allow designers to automatically verify that systems satisfy requirements expressed in ctl. Recently, ctl was generalised by Alur, Henzinger, and Kupferman in a logic known as "Alternating-time Temporal Logic" (atl). The key insight in atl is that the path quantifiers of ctl could be replaced by "cooperation modalities", of the form where # is a set of agents. The intended interpretation of an atl formula is that the agents # can cooperate to ensure that # holds (equivalently, that # have a winning strategy for #). In this paper, we extend atl with knowledge modalities, of the kind made popular in the work of Fagin, Halpern, Moses, Vardi and colleagues. Combining these knowledge modalities with atl, it becomes possible to express such properties as "group # can cooperate to bring about # i# it is common knowledge in # that #". The resulting logic --- Alternating-time Temporal Epistemic Logic (atel) --- shares the tractability of model checking with its atl parent, and is a succinct and expressive language for reasoning about game-like multiagent systems.

We propose a context-logic style formalism, Timed Reasoning Logics (TRL), to describe resource-bounded reasoners who take time to derive consequences of their knowledge. The semantics of TRL is grounded in the agent's computation, allowing an unambiguous ascription of the set of formulas which the agent actually knows at time t. We show that TRL can capture various rule application and conflict resolution strategies that a rule-based agent may employ, and analyse two examples in detail: TRL(STEP) which models an all rules at each cycle strategy similar to that assumed in step logic [4], and TRL(CLIPS) which models a single rule at each cycle strategy similar to that employed by the CLIPS [21] rule based system architecture. We prove a general completeness and decidability results for TRL(STEP).

Abstract. Argumentation has received steadily increasing attention in the multi-agent systems community over the past decade, with particular interest in the use of argument models from the informal logic community. The formalisation of such argument systems is a necessary step if they are to be successfully deployed, and their properties rigorously understood. However, there is as yet no widely accepted approach to the formalisation of argument systems. In this paper, we take as our starting point the view that arguments and dialogues are inherently meta-logical, and that any proper formalisation of argument must embrace this aspect of their nature. For example, a statement that serves as a justification of an argument is is statement about an argument: the argument for which the justification serves must itself be referred to in the justification. From this starting position, we develop a formalisation of arguments using a hierarchical first-order meta-logic, in which statements in successively higher tiers of the argumentation hierarchy refer to statements further down the hierarchy. This enables us to give a clean formal separation between object-level statements, arguments made about these object level statements, and statements about arguments. 1

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Abstract. Practical reasoners are resource-bounded—in particular they require time to derive consequences of their knowledge. Building on the Timed Reasoning Logics (TRL) framework introduced in [1], we show how to represent the time required by an agent to reach a given conclusion. TRL allows us to model the kinds of rule application and conflict resolution strategies commonly found in rule-based agents, and we show how the choice of strategy can influence the information an agent can take into account when making decisions at a particular point in time. We prove general completeness and decidability results for TRL, and analyse the impact of communication in an example system consisting of two agents which use different conflict resolution strategies. 1

Rule-based agents (for example, agents reasoning using ontology rules) are increasingly being employed in the implementation of web services and other situations in which the time taken to generate a response is critical. To be able to provide a response time guarantee for such systems, it is important to know how long the agent’s reasoning is going to take. In this paper, we describe an approach to establishing an upper bound on deliberation time of a system of rule-based agents. We propose a formal model of a system of rule-based agents which associates explicit costs with each rule application. This formal model can serve as an input to a model-checker, allowing upper bounds on deliberation time to be automatically verified. 1

Syntactic logics do not suffer from the problems of logical omniscience but are often thought to lack interesting properties relating to epistemic notions. By focusing on the case of rule-based agents, I develop a framework for modelling resource-bounded agents and show that the resulting models have a number of interesting properties.

Om en semantik för aktiv logik

This paper concerns formal theories for reasoning about the knowledge and belief of agents. It has seemed attractive to researchers in artificial intelligence to formalise these propositional attitudes as predicates of first-order predicate logic. This allows the agents to express stronger introspective beliefs and engage in stronger meta-reasoning than in the classical modal operator approach. Results by Montague [1963] and Thomason [1980] show, however, that the predicate approach is prone to inconsistency.

We present a formalism for representing the intentions of agents engaged in cooperative planning and acting. We focus on cases where one agent alone cannot accomplish a complex task and must subcontract with other agents. Evolving intentions over time during the planning and acting, and the conditions under which an agent can adopt and maintain an intention, are central. In particular, the time taken to plan and to subcontract are modeled explicitly in the logic. This explicit time-representation is used to account for the time it takes an agent to adopt an intention. We use a syntactic approach presenting a formal logical calculus that can be regarded as a meta-logic that describes the reasoning and activities of the agents. We write some of the axioms of this metalanguage and explain the minimal model semantics, in which one model, the intended model, represents the actual beliefs, intentions, and actions of the agents. We also prove several results showing that under the appropriate conditions the agents will act as expected.