Using Event Calculus to Formalise Policy Specification and Analysis

As the interest in using policy-based approaches for systems management grows, it is becoming increasingly important to develop methods for performing analysis and refinement of policy specifications. Although this is an area that researchers have devoted some attention to, none of the proposed solutions address the issues of analysing specifications that combine authorisation and management policies; analysing policy specifications that contain constraints on the applicability of the policies; and performing a priori analysis of the specification that will both detect the presence of inconsistencies and explain the situations in which the conflict will occur. We present a method for transforming both policy and system behaviour specifications into a formal notation that is based on event calculus. Additionally it describes how this formalism can be used in conjunction with abductive reasoning techniques to perform a priori analysis of policy specifications for the various conflict types identified in the literature. Finally, it presents some initial thoughts on how this notation and analysis technique could be used to perform policy refinement

Logic-Based Specification Languages for Intelligent Software Agents

The research field of Agent-Oriented Software Engineering (AOSE) aims to find abstractions, languages, methodologies and toolkits for modeling, verifying, validating and prototyping complex applications conceptualized as Multiagent Systems (MASs). A very lively research sub-field studies how formal methods can be used for AOSE. This paper presents a detailed survey of six logic-based executable agent specification languages that have been chosen for their potential to be integrated in our ARPEGGIO project, an open framework for specifying and prototyping a MAS. The six languages are ConGoLog, Agent-0, the IMPACT agent programming language, DyLog, Concurrent METATEM and Ehhf. For each executable language, the logic foundations are described and an example of use is shown. A comparison of the six languages and a survey of similar approaches complete the paper, together with considerations of the advantages of using logic-based languages in MAS modeling and prototyping.Comment: 67 pages, 1 table, 1 figure. Accepted for publication by the Journal "Theory and Practice of Logic Programming", volume 4, Maurice Bruynooghe Editor-in-Chie

Reasoning techniques for analysis and refinement of policies for service management

The work described in this technical report falls under the general problem of developing methods that would allow us to engineer software systems that are reliable and would offer a certain acceptable level of quality in their operation. This report shows how the analysis and refinement of policies for Quality of Service can be carried out within logic by exploiting forms of abductive and argumentative reasoning. In particular, it provides two main contributions. The first is an extension of earlier work on the use of abductive reasoning for automatic policy refinement by exploiting the use of integrity constraints within abduction and its integration with constraint solving. This has allowed us to enhance this refinement process in various ways, e.g. supporting parameter values derivation to quantify abstract refinement to specific policies ready to be put in operation, and calculating utility values to determine optimal refined policies. The second contribution is a new approach for modelling and formulating Quality of Service policies, and more general policies for software requirements, as preference policies within logical frameworks of argumentation. This is shown to be a flexible and declarative approach to the analysis of such policies through high-level semantic queries of argumentation, demonstrated here for the particular case of network firewall policies where the logical framework of argumentation allows us to detect anomalies in the firewalls and facilitates the process of their resolution. To our knowledge this is the first time that the link between argumentation and the specification and analysis of requirement policies has been studied

Event-internal modifiers : semantic underspecification and conceptual interpretation

The article offers evidence that there are two variants of adverbial modification that differ with respect to the way in which a modifier is linked to the verbs eventuality argument. So-called event-external modifiers relate to the full eventuality, whereas event-internal modifiers relate to some integral part of it. The choice between external and internal modification is shown to be dependent on the modifiers syntactic base position. Event-external modifiers are base-generated at the VP periphery, whereas event-internal modifiers are base-generated at the V periphery. These observations are accounted for by a refined version of the standard Davidsonian approach to adverbial modification according to which modification is mediated by a free variable. In the case of external modification, the grammar takes responsibility for identifying the free variable with the verbs eventuality argument, whereas in the case of internal modification, a value for the free variable is determined by the conceptual system on the basis of contextually salient world knowledge. For the intriguing problem that certain locative modifiers occasionally seem to have nonlocative (instrumental, positional, or manner) readings, the advocated approach can provide a rather simple solution

State-of-the-art on evolution and reactivity

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in Rewerse. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks

Coherent Integration of Databases by Abductive Logic Programming

We introduce an abductive method for a coherent integration of independent data-sources. The idea is to compute a list of data-facts that should be inserted to the amalgamated database or retracted from it in order to restore its consistency. This method is implemented by an abductive solver, called Asystem, that applies SLDNFA-resolution on a meta-theory that relates different, possibly contradicting, input databases. We also give a pure model-theoretic analysis of the possible ways to `recover' consistent data from an inconsistent database in terms of those models of the database that exhibit as minimal inconsistent information as reasonably possible. This allows us to characterize the `recovered databases' in terms of the `preferred' (i.e., most consistent) models of the theory. The outcome is an abductive-based application that is sound and complete with respect to a corresponding model-based, preferential semantics, and -- to the best of our knowledge -- is more expressive (thus more general) than any other implementation of coherent integration of databases