Giacomo Terreni

The CIFF Proof Procedure for Abductive Logic Programming with Constraints

We introduce a new proof procedure for abductive logic programming and present two soundness results. Our procedure extends that of Fung and Kowalski by integrating abductive reasoning with constraint solving and by relaxing the restrictions on allowed inputs for which the procedure can operate correctly. An implementation of our proof procedure is available and has been applied successfully in the context of multiagent systems.

The KGP model of agency for global computing: computational model and prototype implementation

We present the computational counterpart of the KGP (Knowledge, Goals, Plan) declarative model of agency for Global Computing. In this context, a computational entity is seen as an agent developed using Computational Logic tools and techniques. We model a KGP agent by relying upon a collection of capabilities, which are then used to define a collection of transitions, to be used within logically specified, context sensitive control theories, which we call cycle theories. In close relationship to the declarative model, the computational model mirrors the logical architecture by specifying appropriate computational counterparts for the capabilities and using these to give the computational models of the transitions. These computational models and the one specified for the cycle theories are all based on, and are significant extensions of, existing proof procedures for abductive logic programming and logic programming with priorities. We also discuss a prototype implementation of the overall computational model for KGP.

The ciff proof procedure for abductive logic programming with constraints: Theory, implementation and experiments

We present the CIFF proof procedure for abductive logic programming with constraints, and we prove its correctness. CIFF is an extension of the IFF proof procedure for abductive logic programming, relaxing the original restrictions over variable quantification (allowedness conditions) and incorporating a constraint solver to deal with numerical constraints as in constraint logic programming. Finally, we describe the CIFF system, comparing it with state-of-the-art abductive systems and answer set solvers and showing how to use it to program some applications.

Planning partially for situated agents

In recent years, within the planning literature there has been a departure from approaches computing total plans for given goals, in favour of approaches computing partial plans. Total plans can be seen as (partially ordered) sets of actions which, if executed successfully, would lead to the achievement of the goals. Partial plans, instead, can be seen as (partially ordered) sets of actions which, if executed successfully, would contribute to the achievement of the goals, subject to the achievement of further sub-goals. Planning partially (namely computing partial plans for goals) is useful (or even necessary) for a number of reasons: (i) because the planning agent is resource-bounded, (ii) because the agent has incomplete and possibly incorrect knowledge of the environment in which it is situated, (iii) because this environment is highly dynamic. In this paper, we propose a framework to design situated agents capable of planning partially. The framework is based upon the specification of planning problems via an abductive variant of the event calculus.

Abductive Logic Programming with CIFF: System Description

Abduction has long been recognised as a powerful mechanism for hypothetical reasoning in the presence of incomplete knowledge. Here, we discuss the implementation of a novel abductive proof procedure, which we call CIFF, as it extends the IFF proof procedure [7] by dealing with Constraints, as in constraint logic programming.

Web Sites Repairing through Abduction

We present a methodology and a tool for suggesting repairs to web sites that violate some given requirements in the form of web rules expressed in (an extension of) a fragment of Excerpt. The methodology consists in translating these web rules into abductive logic programs with constraints and process these by means of an existing general-purpose proof procedure, called CIFF. The tool, that we call CIFFWEB, consists of CIFF as well as the translation from rules to programs and from web sites to a suitable logical format. The tool extends an existing tool for simply checking web sites against web rules.

An Abductive Proof Procedure Handling Active Rules

We present a simple, though powerful extension of an abductive proof procedure proposed in the literature, the so-called KM-procedure, which allows one to properly treat more general forms of integrity constraints than those handled by the original procedure. These constraints are viewed as active rules, and their treatment allows the integration of a limited form of forward reasoning within the basic, backward reasoning framework upon which the KM-procedure is based. We first provide some background on Abductive Logic Programming and the KM-procedure and then formally present the extension, named AKM-procedure. The usefulness of the extension is shown by means of some simple examples.

Web sites verification: an abductive logic programming tool

We present the CIFFWEB system, an innovative tool for the verification of web sites, relying upon abductive logic programming. The system allows the user to define rules that a web site should fulfill by using (a fragment of) the query language Xcerpt. The rules are translated into abductive logic programs with constraints and their fulfillment is checked through the CIFF abductive proof procedure.

Programming applications in CIFF

We show how to deploy the CIFF System 4.0 for abductive logic programming with constraints in a number of applications, ranging from combinatorial applications to web management. We also compare the CIFF System 4.0 with a number of logic programming tools, namely the A-System, the DLV system and the SMODELS system.