Modal tableaux for verifying stream authentication protocols

To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for the resulting fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments

Modal Tableaux for Verifying Security Protocols

To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for a fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments

Querying Clocked Databases

. We propose a temporal extension of Datalog which can be used to model and query temporal databases with relations based on multiple clocks. The extension, called Clocked Temporal Datalog, is based on a clocked temporal logic in which each predicate and hence each formula can be assigned a separate clock. A Clocked Temporal Datalog program consists of three parts: (1) a clock definition, (2) a clock assignment, and (3) a program body. The clock definition specifies all the available clocks. The clock assignment assigns to each predicate defined in the program body a clock from the clock definition. The meaning of the program body naturally depends on the provided clock definition and assignment. Therefore a Clocked Temporal Datalog program models intensionally a clocked database in which each relation is defined over a clock. Programmable clock definitions are very flexible in specifying periodic as well as some nonperiodic clocks, and in specifying relationships between clocks on the..

Towards security labelling

Security labels are applied for numerous reasons, including the handling of data communicated between open systems. The information contained within a security label can be utilised to perform access control decisions, specify protective measure, and aid in the determination of additional handling restrictions required by a communications security policy. This paper concerns the issues regarding security labelling in open systems. We propose a security labelling framework for such systems; and further, based on this framework, we develop a mechanically checkable model for security labelling systems and discuss its implementation issues. This model provides a functional base for future design and implementation of security labelling systems.8 page(s

Dealing with Multiple Granularity of Time in Temporal Logic Programming

Chronolog(MC) is an extension of logic programming based on a clocked temporal logic (CTL), a linear-time temporal logic with multiple granularity of time. A Chronolog(MC) program consists of a clock definition, a clock assignment and a program body, and each predicate symbol appearing in the program body is associated with a local clock through the clock definition and assignment. This paper investigates the logical basis of the language, presents a clocked temporal resolution where time-matching is essential, and in particular proposes three algorithms for time-matching. The paper also discusses the declarative semantics for Chronolog(MC) programs in terms of clocked temporal Herbrand models. It is shown that Chronolog(MC) programs also satisfy the minimum model semantics. The language can be used to model a wide range of simulation systems and other relevant tasks where the notion of dynamic change is central

Fibred belief logic for multi-agent systems

Multi-agent systems consist of a number of autonomous agents (software programs) that are capable of independent action on behalf of their users. Agents communicate with one another by exchanging messages, and they have the ability to co-operate, co-ordinate and negotiate with each other to achieve their objectives. In order to develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we consider a powerful technique called fibring for combining belief logics and temporal logics. In a fibred belief logic, both temporal operators and belief operators are treated equally. This paper in particular discusses a combination of a belief logic called Typed-Modal Logic with a linear-time temporal logic. We show that, in the resulting logic, we can specify and reason about not only agents’ beliefs but also the timing properties of a system. With this logical system one is able to build theories of trust for the description of, and reasoning about, multi-agent systems.1 page(s

Clocked Temporal Logic Programming

Clocked temporal logic programming(CTLP) is an extension of logic programming based on a clocked temporal logic(CTL). In CTL, predicates are associated with local clocks. Local clocks can be used to model multiple granularity of time, thus the resulting temporal logic programming language, called Chronolog(MC), has a stronger modeling power. This paper discusses the logical basis of the language and outlines its operational semantics. Also, a parallel execution model for Chronolog(MC) programs is outlined. An application of CTLP to distributed computations is discussed. Keywords Temporal logic, Logic programming, Clocks, Temporal resolution, Parallel execution. 1 Introduction An important activity in computer science is the invention, analysis and application of formal logics which are designed to specify, reason about and represent algorithms, programs and systems. For instance, temporal logic has been widely used as a formalism for program specification and verification [12, 3], r..

Reasoning about dynamics of trust and agent beliefs

Many formal frameworks have been proposed for specifying and reasoning about the notion of trust and trust mechanisms in agent-based systems. Typed modal logic (TML) is a logic of beliefs which is suitable for the description of, and reasoning about, trust for multi-agent systems by formalising trust policies of the system and agent meta-beliefs in its security mechanisms. In this paper, by adopting the methodology of Finger and Gabbay for temporalising a logic system, we combine TML with a temporal logic, so that the users can also model evolving theories of trust. In the resulting logic, denoted by TML+, temporal properties of trust and agent beliefs can be expressed in a natural way by combinations of temporal and modal belief operators.6 page(s

A Parallel Execution Model for Chronolog

Chronolog(Z) is a logic programming language based on a linear-time temporal logic with unbounded past and future. By adding "choice predicates" to Chronolog(Z), it is possible to obtain exactly one answer to a given goal when we want to model dataflow style of stream-oriented computations. This paper, based on the framework we propose for exploiting parallelism in Chronolog, discusses and enhances the parallel execution model CHEM so that it is suitable for Chronolog(Z) programs with choice predicates. Dealing with the inherent context-parallelism in Chronolog programs, we propose the concept of parallel context-processes. We also introduce an intermediate virtual machine (CVM), which is granulated to exploit the argument parallelism through temporal unification. The details of the CVM instruction set are given in this paper. The use of a warehouse facility as an associate memory to store the results of previous computations is an important feature of this model. This paper..