Wiebe van der Hoek

Dynamic Epistemic Logic

The appendix to the chapter on dynamics supplements the chapter with an overview of dynamic epistemic logic: a branch of logic mainly developed in the decade after the first edition of this handbook was published. Dynamic epistemic logic is an extension of epistemic logic (the logic of knowledge), which focusses on information change, such as communication, usually involving more than one agent. The information of the agents includes information about each others information, socalled higher-order information. The appendix consists of three parts. In the first part an example scenario is presented which can be captured by dynamic epistemic logic. The second part is a historical overview of the main approaches in dynamic epistemic logic is presented. The last part is a look towards the future which attempts to connect ideas from dynamic approaches to language with dynamic epistemic logic.

Agent Programming in 3APL

An intriguing and relatively new metaphor in the programming community is that of an intelligent agent. The idea is to view programs as intelligent agents acting on our behalf. By using the metaphor of intelligent agents the programmer views programs as entities which have a mental state consisting of beliefs and goals. The computational behaviour of an agent is explained in terms of the decisions the agent makes on the basis of its mental state. It is assumed that this way of looking at programs may enhance the design and development of complex computational systems.To support this new style of programming, we propose the agent programming language 3APL. 3APL has a clear and formally defined semantics. The operational semantics of the language is defined by means of transition systems. 3APL is a combination of imperative and logic programming. From imperative programming the language inherits the full range of regular programming constructs, including recursive procedures, and a notion of state-based computation. States of agents, however, are belief or knowledge bases, which are different from the usual variable assignments of imperative programming. From logic programming, the language inherits the proof as computation model as a basic means of computation for querying the belief base of an agent. These features are well-understood and provide a solid basis for a structured agent programming language. Moreover, on top of that 3APL agents use so-called practical reasoning rules which extend the familiar recursive rules of imperative programming in several ways. Practical reasoning rules can be used to monitor and revise the goals of an agent, and provide an agent with reflective capabilities.Applying the metaphor of intelligent agents means taking a design stance. From this perspective, a program is taken as an entity with a mental state, which acts pro-actively and reactively, and has reflective capabilities. We illustrate how the metaphor of intelligent agents is supported by the programming language. We also discuss the design of control structures for rule-based agent languages. A control structure provides a solution to the problem of which goals and which rules an agent should select. We provide a concrete and intuitive ordering on the practical reasoning rules on which such a selection mechanism can be based. The ordering is based on the metaphor of intelligent agents. Furthermore, we provide a language with a formal semantics for programming control structures. The main idea is not to integrate this language into the agent language itself, but to provide the facilities for programming control structures at a meta level. The operational semantics is accordingly specified at the meta level, by means of a meta transition system.

Cooperation, knowledge, and time: Alternating-time temporal epistemic logic and its applications

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 《Γ》, where Γ is a set of agents. The intended interpretation of an ATL formula 《Γ》ϕ is that the agents Γ can cooperate to ensure that ϕ holds (equivalently, that Γ have a winning strategy for ϕ). 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 Γ can cooperate to bring about ϕ iff it is common knowledge in Γ that ψ”. 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.

Tractable multiagent planning for epistemic goals

An epistemic goal is a goal about the knowledge possessed by an agent or group of agents. In this paper, we address the problem of how plans might be developed for a group of agents to cooperate to bring about such a goal. We present a novel approach to this problem, in which the problem is formulated as one of model checking in Alternating Temporal Epistemic Logic (ATEL). After introducing this logic, we present a model checking algorithm for it, and show that the model checking problem for this logic is tractable. We then show how multiagent planning can be treated as a model checking problem in ATEL, and discuss the related issue of checking knowledge preconditions for multiagent plans. We illustrate the approach with an example. We then describe how this example was implemented using the MOCHA model checking system, and conclude by discussing the relationship of our work with that of others in the planning and speech acts communities.

SOFSEM 2007: Theory and Practice of Computer Science

Invited Talks.- Graphs from Search Engine Queries.- Model-Checking Large Finite-State Systems and Beyond.- Interaction and Realizability.- A Short Introduction to Computational Social Choice.- Distributed Models and Algorithms for Mobile Robot Systems.- Point-to-Point Shortest Path Algorithms with Preprocessing.- Games, Time, and Probability: Graph Models for System Design and Analysis.- Agreement Technologies.- Automatic Testing of Object-Oriented Software.- Architecture-Based Reasoning About Performability in Component-Based Systems.- Multimedia Retrieval Algorithmics.- Foundations of Computer Science.- Size of Quantum Finite State Transducers.- Weighted Nearest Neighbor Algorithms for the Graph Exploration Problem on Cycles.- Straightening Drawings of Clustered Hierarchical Graphs.- Improved Upper Bounds for ?-Backbone Colorings Along Matchings and Stars.- About the Termination Detection in the Asynchronous Message Passing Model.- Fast Approximate Point Set Matching for Information Retrieval.- A Software Architecture for Shared Resource Management in Mobile Ad Hoc Networks.- Compressed Prefix Sums.- On Optimal Solutions for the Bottleneck Tower of Hanoi Problem.- Competitive Maintenance of Minimum Spanning Trees in Dynamic Graphs.- Exact Max 2-Sat: Easier and Faster.- Maximum Finding in the Symmetric Radio Networks with Collision Detection.- An Approach to Modelling and Verification of Component Based Systems.- Improved Undecidability Results on the Emptiness Problem of Probabilistic and Quantum Cut-Point Languages.- On the (High) Undecidability of Distributed Synthesis Problems.- Maximum Rigid Components as Means for Direction-Based Localization in Sensor Networks.- Online Service Management Algorithm for Cellular/WALN Multimedia Networks.- A Simple Algorithm for Stable Minimum Storage Merging.- Generating High Dimensional Data and Query Sets.- Partial vs. Complete Domination: t-Dominating Set.- Estimates of Data Complexity in Neural-Network Learning.- Concurrent and Located Synchronizations in ?-Calculus.- Efficient Group Key Agreement for Dynamic TETRA Networks.- Algorithmic Aspects of Minimum Energy Edge-Disjoint Paths in Wireless Networks.- The P k Partition Problem and Related Problems in Bipartite Graphs.- Spatial Selection of Sparse Pivots for Similarity Search in Metric Spaces.- A Model of an Amorphous Computer and Its Communication Protocol.- A Branch-and-Bound Algorithm to Solve Large Scale Integer Quadratic Multi-Knapsack Problems.- Indexing Factors with Gaps.- Information Efficiency.- Deterministic Simulation of a NFA with k-Symbol Lookahead.- Mobility Management Using Virtual Domain in IPv6-Based Cellular Networks.- Restarting Tree Automata.- A Polynomial Time Constructible Hitting Set for Restricted 1-Branching Programs of Width 3.- Formal Translation Directed by Parallel LLP Parsing.- Self-adaptive Lagrange Relaxation Algorithm for Aggregated Multicast.- A Language for Reliable Service Composition.- Operational Semantics of Framed Temporal Logic Programs.- Constraints for Argument Filterings.- Multi-agent Systems.- Performance Analysis of a Multiagent Architecture for Passenger Transportation.- Teacher-Directed Learning with Mixture of Experts for View-Independent Face Recognition.- FTTH-Enhanced Mini-System m TBCP-Based Overlay Construction and Evaluation.- On Efficient Resource Allocation in Communication Networks.- Protecting Agent from Attack in Grid ComputingIII.- Incremental Learning of Planning Operators in Stochastic Domains.- Competitive Contract Net Protocol.- Agent Oriented Methodology Construction and Customization with HDA.- Emerging Web Technologies.- Building an Ontological Base for Experimental Evaluation of Semantic Web Applications.- Semantic Web Approach in Designing a Collaborative E-Item Bank System.- A Hybrid Region Weighting Approach for Relevance Feedback in Region-Based Image Search on the Web.- Rapid Development of Web Interfaces to Heterogeneous Systems.- Enhancing Security by Embedding Biometric Data in IP Header.- Runtime-Efficient Approach for Multiple Continuous Filtering in XML Message Brokers.- A Semantic Peer-to-Peer Overlay for Web Services Discovery.- Multi-document Summarization Based on Cluster Using Non-negative Matrix Factorization.- A Program Slicing Based Method to Filter XML/DTD Documents.- A Hybrid Approach for XML Similarity.- Personalized Presentation in Web-Based Information Systems.- Immune-Inspired Online Method for Service Interactions Detection.- Dependable Software and Systems.- Separation of Concerns and Consistent Integration in Requirements Modelling.- Checking Interaction Consistency in MARMOT Component Refinements.- Towards a Versatile Contract Model to Organize Behavioral Specifications.- Improved Processing of Textual Use Cases: Deriving Behavior Specifications.- A Dialogue-Based NLIDB System in a Schedule Management Domain.- Experimental Assessment of the Practicality of a Fault-Tolerant System.- A Polynomial-Time Checkable Sufficient Condition for Deadlock-Freedom of Component-Based Systems.- Extracting Zing Models from C Source Code.- Parameterised Extra-Functional Prediction of Component-Based Control Systems - Industrial Experience.- Explicit Connectors in Component Based Software Engineering for Distributed Embedded Systems.

Agent Programming with Declarative Goals

A long and lasting problem in agent research has been to close the gap between agent logics and agent programming frameworks. The main reason for this problem of establishing a link between agent logics and agent programming frameworks is identified and explained by the fact that agent programming frameworks have not incorporated the concept of a declarative goal. Instead, such frameworks have focused mainly on plans or goals-to-do instead of the end goals to be realised which are also called goals-to-be. In this paper, a new programming language called GOAL is introduced which incorporates such declarative goals. The notion of a commitment strategy - one of the main theoretical insights due to agent logics, which explains the relation between beliefs and goals - is used to construct a computational semantics forGOAL. Finally, a proof theory for proving properties of GOAL agents is introduced. An example program is proven correct by using this programming logic.

On the logic of cooperation and propositional control

Cooperation logics have recently begun to attract attention within the multi-agent systems community. Using a cooperation logic, it is possible to represent and reason about the strategic powers of agents and coalitions of agents in game-like multi-agent systems. These powers are generally assumed to be implicitly defined within the structure of the environment, and their origin is rarely discussed. In this paper, we study a cooperation logic in which agents are each assumed to control a set of propositional variables--the powers of agents and coalitions then derive from the allocation of propositions to agents. The basic modal constructs in this Coalition Logic of Propositional Control (CL-PC) allow us to express the fact that a group of agents can cooperate to bring about a certain state of affairs. After motivating and introducing CL-PC, we provide a complete axiom system for the logic, investigate the issue of characterising control in CL-PC with respect to the underlying power structures of the logic, and formally investigate the relationship between CL-PC and Paulys Coalition Logic. We then show that the model checking and satisfiability problems for CL-PC are both PSPACE-complete, and conclude by discussing our results and how CL-PC sits in relation to other logics of cooperation.

Model Checking Knowledge and Time

Model checking as an approach to the automatic verification of finite state systems has focussed predominantly on system specifications expressed in temporal logic. In the distributed systems community, logics of knowledge (epistemic logics) have been advocated for expressing desirable properties of protocols and systems. A range of logics combining temporal and epistemic components have been developed for this purpose. However, the model checking problem for temporal logics of knowledge has received (comparatively) little attention. In this paper, we address ourselves to this problem. Following a brief survey of the relevant issues and literature, we introduce a temporal logic of knowledge (Halpern and Vardis logic CKLn). We then develop an approach to CKLn model checking that combines ideas from the interpreted systems semantics for knowledge with the logic of local propositions developed by Engelhardt et al. With our approach, local propositions provide a means to reduce CKLn model checking to linear temporal logic model checking. After introducing and exploring the ideas underpinning our approach, we present a case study (the bit transmission problem) in which spin was used to establish temporal epistemic properties of a system implemented in promela.

Towards a Logic of Rational Agency

Rational agents are important objects of study in several research communities, including economics, philosophy, cognitive science, and most recently computer science and artificial intelligence. Crudely, a rational agent is an entity that is capable of acting on its environment, and which chooses to act in such a way as to further its own best interests. There has recently been much interest in the use of mathematical logic for developing formal theories of such agents. Such theories view agents as practical reasoning systems, deciding moment by moment which action to perform next, given the beliefs they have about the world and their desires with respect to how they would like the world to be. In this article, we survey the state of the art in developing logical theories of rational agency. Following a discussion on the dimensions along which such theories can vary, we briefly survey the logical tools available in order to construct such theories. We then review and critically assess three of the best known theories of rational agency: Cohen and Levesque’s intention logic, Rao and Georgeff’s bdi logics, and the KARO framework of Meyer et al. We then discuss the various roles that such logics can play in helping us to engineer rational agents, and conclude with a discussion of open problems.

Social laws in alternating time: effectiveness, feasibility, and synthesis

Since it was first proposed by Moses, Shoham, and Tennenholtz, the social laws paradigm has proved to be one of the most compelling approaches to the offline coordination of multiagent systems. In this paper, we make four key contributions to the theory and practice of social laws in multiagent systems. First, we show that the Alternating-time Temporal Logic (atl) of Alur, Henzinger, and Kupferman provides an elegant and powerful framework within which to express and understand social laws for multiagent systems. Second, we show that the effectiveness, feasibility, and synthesis problems for social laws may naturally be framed as atl model checking problems, and that as a consequence, existing atl model checkers may be applied to these problems. Third, we show that the complexity of the feasibility problem in our framework is no more complex in the general case than that of the corresponding problem in the Shoham–Tennenholtz framework (it is np-complete). Finally, we show how our basic framework can easily be extended to permit social laws in which constraints on the legality or otherwise of some action may be explicitly required. We illustrate the concepts and techniques developed by means of a running example.