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1

Negation as a Resource: a Novel View on Answer Set Semantics

Costantini S., Formisano A.

Fundamenta Informaticae

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2015

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Vol. 140, nr 3/4

279--305

EN

In recent work, we provided a formulation of ASP programs in terms of linear logic theories. Answer sets were characterized in terms of maximal tensor conjunctions provable from such theories. In this paper, we propose a full comparison between Answer Set Semantics and its variation obtained by interpreting literals (including negative literals) as resources, which leads to a different interpretation of negation. We argue that this novel view can be of both theoretical and practical interest, and we propose a modified Answer Set Semantics that we call Resource-based Answer Set Semantics. An advantage is that of avoiding inconsistencies, as every program has a (possibly empty) resource-based answer set. This implies however the introduction of a different way of representing constraints. We provide a characterization of the new semantics as a variation of the answer set semantics, and also in terms of Autoepistemic Logic. The latter characterization leads to a way of computing resource-based answer set via answer set solvers.

2

Product and Production Process Modeling and Configuration

Campagna D., Formisano A.

Fundamenta Informaticae

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2013

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Vol. 124, nr 4

403--425

EN

Product configuration systems are an emerging technology that supports companies in deploying mass customization strategies. Such strategies need to cover the management of the whole customizable product cycle. Adding process modeling and configuration features to a product configurator may improve its ability to assist mass customization development. In this paper, we describe a modeling framework, PRODPROC, that allows one to model both a product and its production process. We first introduce our framework by describing how configurable products are modeled. Then, we describe the main features and capabilities offered to model production processes and to link them with the corresponding products models. The configuration task (namely, the procedure that, from a configurable object/activity generates a configured product/process) is then analyzed. We also outline a possible CSP-based implementation of a configurator. A comparison with some of the existing systems for product configuration and process modeling emphasizes that none of the considered system/tools offers the complete set of features supported by PRODPROC for interdependent product and process modeling/configuration.

3

Nested Weight Constraints in ASP

Costantini S., Formisano A.

Fundamenta Informaticae

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2013

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Vol. 124, nr 4

449--464

EN

Weight constraints are a powerful programming construct that has proved very useful within the Answer Set Programming paradigm. In this paper, we argue that practical Answer Set Programming might take profit from introducing some forms of nested weight constraints. We define such empowered constraints (that we call 'Nested Weight Constraints') and discuss their semantics and their complexity.

4

Extending and Implementing RASP

Costantini S., Formisano A., Petturiti D.

Fundamenta Informaticae

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2011

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Vol. 105, nr 1/2

1-33

EN

In previous work we have proposed an extension to ASP (Answer Set Programming), called RASP, standing for ASP with Resources. RASP supports declarative reasoning on production and consumption of (amounts of) resources. The approach combines answer set semantics with quantitative reasoning and relies on an algebraic structure to support computations and comparisons of amounts. The RASP framework provides some form of preference reasoning on resources usage. In this paper, we go further in this direction by introducing expressive constructs for supporting complex preferences specification on aggregate resources. We present a refinement of the semantics of RASP so as to take into account the new constructs. For all the extensions, we provide an encoding into plain ASP.We prove that the complexity of establishing the existence of an answer set, in such an enriched framework, remains NP-complete as in ASP. Finally, we report on raspberry, a prototypical implementation of RASP. This tool consists of a compiler that, given a ground RASP program, produces a pure ASP encoding suitable to be processed by commonly available ASP-solvers.

5

An Investigation of Multi-Agent Planning in CLP

Dovier A., Formisano A., Pontelli E.

Fundamenta Informaticae

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2011

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Vol. 105, nr 1/2

79-103

EN

This paper explores the use of Constraint Logic Programming (CLP) as a platform for experimenting with planning problems in the presence of multiple interacting agents. The paper develops a novel constraint-based action language, BMAP, that enables the declarative description of large classes of multi-agent and multi-valued domains. BMAP supports several complex features, including combined effects of concurrent and interacting actions, concurrency control, and delayed effects. The paper presents a mapping of BMAP theories to CLP and it demonstrates the effectiveness of an implementation in SICStus Prolog on several benchmark problems. The effort is an evolution of previous research on using CLP for single-agent domains, demonstrating the flexibility of CLP technology to handle the more complex issues of multi-agency and concurrency.