Marco Gavanelli

Verifiable agent interaction in abductive logic programming: The SCIFF framework

SCIFF is a framework thought to specify and verify interaction in open agent societies. The SCIFF language is equipped with a semantics based on abductive logic programming; SCIFFs operational component is a new abductive logic programming proof procedure, also named SCIFF, for reasoning with expectations in dynamic environments. In this article we present the declarative and operational semantics of the SCIFF language, and the termination, soundness, and completeness results of the SCIFF proof procedure, and we demonstrate SCIFFs possible application in the multiagent domain.

COMPLIANCE VERIFICATION OF AGENT INTERACTION: A LOGIC-BASED SOFTWARE TOOL

In open societies of agents, where agents are autonomous and heterogeneous, it is not realistic to assume that agents will always act so as to comply with interaction protocols. Thus, the need arises for a formalism to specify constraints on agent interaction, and for a tool able to observe and check for agent compliance with interaction protocols. In this paper we present a JAVA-PROLOG software component built on logic programming technology, which can be used to verify compliance of agent interaction to protocols, and that has been integrated with the PROSOCS platform.

Expressing and Verifying Business Contracts with Abductive Logic Programming

SCIFF is a declarative language, based on abductive logic programming, that accommodates forward rules, predicate definitions, and constraints over finite domain variables. Its abductive declarative semantics can be related to that of deontic operators; its operational specification is the sound and complete SCIFF proof procedure, defined as a set of transition rules implemented and integrated into a reasoning and verification tool. A variation of the SCIFF proof procedure (g-SCIFF) can be used for static verification of contract properties. The use of SCIFF for business contract specification and verification is demonstrated in a concrete scenario. Encoding of SCIFF contract rules in RuleML accommodates integration of SCIFF with architectures for business contracts.

An abductive framework for a-priori verification of web services

Although stemming from very different research areas, Multi-Agent Systems (MAS) and Service Oriented Computing (SOC) share common topics, problems and settings. One of the common problems is the need to formally verify the conformance of individuals (Agents or Web Services) to common rules and specifications (resp. Protocols/Choreographies), in order to provide a coherent behaviour and to reach the goals of the user.In previous publications, we developed a framework, SCIFF, for the automatic verification of compliance of agents to protocols. The framework includes a language based on abductive logic programming and on constraint logic programming for formally defining the social rules; suitable proof-procedures to check on-the-fly and a-priori the compliance of agents to protocols have been defined.Building on our experience in the MAS area, in this paper we make a first step towards the formal verification of web services conformance to choreographies. We adapt the SCIFF\ framework for the new settings, and propose a heir of SCIFF, the framework AlLoWS (Abductive Logic Web-service Specification).. AlLoWS comes with a language for defining formally a choreography and a web service specification. As its ancestor, AlLoWS has a declarative and an operational semantics. We show examples of how AlLoWS deals correctly with interaction patterns previously identified. Moreover, thanks to its constraint-based semantics, AlLoWS deals seamlessly with other cases involving constraints and deadlines

The log-support encoding of CSP into SAT

Various encodings have been proposed to convert Constraint Satisfaction Problems (CSP) into Boolean Satisfiability problems (SAT). Some of them use a logical variable for each element in each domain: among these very successful are the direct and the support encodings. Other methods, such as the log-encoding, use a logarithmic number of logical variables to encode domains. However, they lack the propagation power of the direct and support encodings, so many SAT solvers perform poorly on log-encoded CSPs. In this paper, we propose a new encoding, called log-support, that combines the log and support encodings. It has a logarithmic number of variables, and uses support clauses to improve propagation. We also extend the encoding using a Gray code. We provide experimental results on Job-Shop scheduling and randomly-generated problems.

Verification from Declarative Specifications Using Logic Programming

In recent years, the declarative programming philosophy has had a visible impact on new emerging disciplines, such as heterogeneous multi-agent systems and flexible business processes. We address the problem of formal verification for systems specified using declarative languages, focusing in particular on the Business Process Management field. We propose a verification method based on the g-SCIFF abductive logic programming proof procedure and evaluate our method empirically, by comparing its performance with that of other verification frameworks.

The SCIFF abductive proof-procedure

We propose an operational framework which builds on the classical understanding of abductive reasoning in logic programming, and extends it in several directions. The new features include the ability to reason with a dynamic knowledge base, where new facts can be added anytime, the ability to generate expectations about such new facts occurring in the future (forecasting), and the process of confirmation/disconfirmation of such expectations.

Modeling Interactions Using Social Integrity Constraints: A Resource Sharing Case Study

Computees are abstractions of the entities situated in global and open computing environments. The societies that they populate give an institutional meaning to their interactions and define the allowed interaction protocols. Social integrity constraints represent a powerful though simple formalism to express such protocols. Using social integrity constraints, it is possible to give a formal definition of concepts such as violation, fulfillment, and social expectation. This allows for the automatic verification of the social behaviour of computees. The aim of this paper is to show by way of a case study how the theoretical framework can be used in practical situations where computees can operate. The example that we choose is a resource exchange scenario.

A social ACL semantics by deontic constraints

In most proposals for multi-agent systems, an Agent Communication Language (ACL) is the formalism designed to express knowledge exchange among agents. However, a universally accepted standard for ACLs is still missing. Among the different approaches to the definition of ACL semantics, the social approach seems the most appropriate to express semantics of communication in open societies of autonomous and heterogeneous agents. In this paper we propose a formalism (deontic constraints) to express social ACL semantics, which can be grounded on a computational logic framework, thus allowing automatic verification of compliance by means of appropriate proof procedures. We also show how several common communication performatives can be defined by means of deontic constraints.

Optimal placement of valves in a water distribution network with CLP(FD)

This paper presents a new application of logic programming to a real-life problem in hydraulic engineering. The work is developed as a collaboration of computer scientists and hydraulic engineers, and applies Constraint Logic Programming to solve a hard combinatorial problem. This application deals with one aspect of the design of a water distribution network, i.e., the valve isolation system design. We take the formulation of the problem by Giustolisi and Savic (2008 Optimal design of isolation valve system for water distribution networks. In Proceedings of the 10th Annual Water Distribution Systems Analysis Conference WDSA2008 , J. Van Zyl, A. Ilemobade, and H. Jacobs, Eds.) and show how, thanks to constraint propagation, we can get better solutions than the best solution known in the literature for the Apulian distribution network. We believe that the area of the so-called hydroinformatics can benefit from the techniques developed in Constraint Logic Programming and possibly from other areas of logic programming, such as Answer Set Programming.