Abstract. 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.
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
Abstract. 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.
Web Checking RulesThe exponential growth of the WWW raises the question of maintaining and repairing automatically web pages at both structural and data level. Our web checking rules are characterized by using (a fragment of) the query language Xcerpt [2] for expressing complex queries in a natural syntax. Web checking rules are specified by a condition part (starting with FROM) and an error part (starting with GOAL). The intuitive meaning of a rule is that for each instance in the XML resource(s) matching the condition part, an error needs to be returned. Due to lack of space, the example does not cover the whole expressiveness of our rules: in particular the absence of XML data (without construct) and (arithmetical) constraints over variables can also be expressed. However, to the best of our knowledge, Xcerpt lacks of both a clear semantics for negation constructs (without) and a concrete tool for evaluating Xcerpt queries. Hence, we map web checking rules into abductive logic programs with constraints (ALPCs) that can be fed as input to the CIFF System 4.0, an implementation of the general-purpose CIFF abductive proof procedure [3] which is sound with respect to the 3-valued completion semantics. Using CIFF for determining the fulfillment of the rules, we inherit its formal properties, thus obtaining a sound concrete tool for web sites verification.
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