Reasoning about Choice

We present a logic for reasoning about choice. Choice ctl (c-ctl) extends the well-known branching-time temporal logic ctl with choice modalities, " ◊ " and "□". An example c-ctl formula is ◊ AF happy, asserting that there exists a choice that will lead to happiness. c-ctl is related to both stit logics and temporal cooperation logics such as atl, but has a much simpler and (we argue) more intuitive syntax and semantics. After presenting the logic, we investigate the properties of the language. We characterise the complexity of the c-ctl model checking problem, investigate some validities, and propose multi-agent extensions to the logic

Grounding power on actions and mental attitudes

International audienceThe main objective of this work is to develop a logic called IAL (Intentional Agency Logic) in which we can reason about mental states of agents, action occurrences, and agentive and group powers. IAL will be exploited for a formal analysis of different forms of power such as an agent i's power of achieving a certain result and an agent i's power over another agent j (alias social power)

A Semantic Approach to Decidability in Epistemic Planning

The use of Dynamic Epistemic Logic (DEL) in multi-agent planning has led to a widely adopted action formalism that can handle nondeterminism, partial observability and arbitrary knowledge nesting. As such expressive power comes at the cost of undecidability, several decidable fragments have been isolated, mainly based on syntactic restrictions of the action formalism. In this paper, we pursue a novel semantic approach to achieve decidability. Namely, rather than imposing syntactical constraints, the semantic approach focuses on the axioms of the logic for epistemic planning. Specifically, we augment the logic of knowledge S5n and with an interaction axiom called (knowledge) commutativity, which controls the ability of agents to unboundedly reason on the knowledge of other agents. We then provide a threefold contribution. First, we show that the resulting epistemic planning problem is decidable. In doing so, we prove that our framework admits a finitary non-fixpoint characterization of common knowledge, which is of independent interest. Second, we study different generalizations of the commutativity axiom, with the goal of obtaining decidability for more expressive fragments of DEL. Finally, we show that two well-known epistemic planning systems based on action templates, when interpreted under the setting of knowledge, conform to the commutativity axiom, hence proving their decidability

Asymmetric Hybrids: Dialogues for Computational Concept Combination

When people combine concepts these are often characterised as “hybrid”, “impossible”, or “humorous”. However, when simply considering them in terms of extensional logic, the novel concepts understood as a conjunctive concept will often lack meaning having an empty extension (consider “a tooth that is a chair”, “a pet flower”, etc.). Still, people use different strategies to produce new non-empty concepts: additive or integrative combination of features, alignment of features, instantiation, etc. All these strategies involve the ability to deal with conflicting attributes and the creation of new (combinations of) properties. We here consider in particular the case where a Head concept has superior ‘asymmetric’ control over steering the resulting concept combination (or hybridisation) with a Modifier concept. Specifically, we propose a dialogical approach to concept combination and discuss an implementation based on axiom weakening, which models the cognitive and logical mechanics of this asymmetric form of hybridisation

Reasoning about actions meets strategic logics (LORI 2013)

International audienceWe introduce ATLEA, a novel extension of Alternating-time Temporal Logic with explicit actions in the object language. ATLEA allows to reason about abilities of agents under commitments to play certain actions. Pre- and postconditions as well as availability and unavailability of actions can be expressed. We show that the multiagent extension of Reiter’s solution to the frame problem can be encoded into ATLEA. We also consider an epistemic extension of ATLEA. We demonstrate that the resulting logic is sufficiently expressive to reason about uniform choices of actions. Complexity results for the satisfiability problem of ATLEA and its epistemic extension are given in the paper

Logics of knowledge and action: critical analysis and challenges

International audienceWe overview the most prominent logics of knowledge and action that were proposed and studied in the multiagent systems literature. We classify them according to these two dimensions, knowledge and action, and moreover introduce a distinction between individual knowledge and group knowledge, and between a nonstrategic an a strategic interpretation of action operators. For each of the logics in our classification we highlight problematic properties. They indicate weaknesses in the design of these logics and call into question their suitability to represent knowledge and reason about it. This leads to a list of research challenges

A resource-sensitive logic of agency

We study a fragment of Intuitionistic Linear Logic combined with non-normal modal operators. Focusing on the minimal modal logic, we provide a Gentzen-style sequent calculus as well as a semantics in terms of Kripke resource models. We show that the proof theory is sound and complete with respect to the class of minimal Kripke resource models. We also show that the sequent calculus allows cut elimination. We put the logical framework to use by instantiating it as a logic of agency. In particular, we apply it to reason about the resource-sensitive use of artefacts

A resource-sensitive account of the use of artifacts

The aim of this abstract is to introduce a formal framework enabling to reason about resource-sensitive uses of artifacts. To achieve this, we integrate (non-normal) modalities into Intuitionistic Linear Logic. The function of an artifact is a (resource-sensitive) linear implication and we interpret each modality as an agent\u2019s bringing about of resources

Perceptron operators that count

The Felony Score Sheet used in the US State of Florida, describes various features of a crime and their assigned points. Features may include ‘possession of cocaine’, or ‘number of caused injuries’. A threshold must be reached to decide compulsory imprisonment. In previous research, we have introduced a perceptron operator for knowledge representation languages. With it, concepts can be defined by listing a concept’s features with associated weights, and a threshold. An individual belongs to such a concept if the weighted sum of the listed features it belongs to reaches the threshold. It can capture the concept of compulsory imprisonment defined by the Felony Score Sheet. However, it suffers some limitations in that one must artificially use concepts like ‘caused one injury’, ‘caused two injuries’, etc, to be able to count. This paper proposes an extension of the perceptron operator to define concepts like the compulsory imprisonment from the Felony Score Sheet faithfully and easily, relying on role-successors counting. We show that when the weights are non-negative, reasoning in ALC augmented with the perceptron operator can be reduced to reasoning in ALCQ. Capitalizing on the recent ALCSCC, we also show that adding the operator to ALC does not affect the complexity of reasoning in general