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Giovanni Guida

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6 papers
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6

AIJ Journal 2005 Journal Article

SCC-recursiveness: a general schema for argumentation semantics

  • Pietro Baroni
  • Massimiliano Giacomin
  • Giovanni Guida

In argumentation theory, Dung's abstract framework provides a unifying view of several alternative semantics based on the notion of extension. In this context, we propose a general recursive schema for argumentation semantics, based on decomposition along the strongly connected components of the argumentation framework. We introduce the fundamental notion of SCC-recursiveness and we show that all Dung's admissibility-based semantics are SCC-recursive, and therefore a special case of our schema. On these grounds, we argue that the concept of SCC-recursiveness plays a fundamental role in the study and definition of argumentation semantics. In particular, the space of SCC-recursive semantics provides an ideal basis for the investigation of new proposals: starting from the analysis of several examples where Dung's preferred semantics gives rise to questionable results, we introduce four novel SCC-recursive semantics, able to overcome the limitations of preferred semantics, while differing in other respects.

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AIJ Journal 2005 Journal Article

Self-stabilizing defeat status computation: dealing with conflict management in multi-agent systems

  • Pietro Baroni
  • Massimiliano Giacomin
  • Giovanni Guida

The role of argumentation in supporting various forms of interaction among possibly conflicting autonomous agents has been explicitly recognized in the literature. In argumentation, conflict management is carried out by the formal process of defeat status computation. In this paper we consider the generalization of this process to a distributed setting. We show that significant stabilization problems may arise even in relatively simple cases. A fundamental negative result is then proved: no general self-stabilizing algorithm exists for distributed defeat status computation, indicating that self-stabilizing algorithms for this problem can be defined only under specific conditions. Accordingly, we focus on two cases: an algorithm tailored to a specific family of inference graphs, that include only rebutting defeaters, and an algorithm that applies to any inference graph, also including undercutting defeaters, but may provide (cautiously) incorrect results for some nodes. For both algorithms the worst-case round complexity is analyzed and it is proved that no algorithms with lower complexity exist for the same tasks.

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AAAI Conference 1986 Conference Paper

Design and Experimentation of an Expert System for Programming In-the-Large

  • Giovanni Guida
  • Sergio Gusmeroli

The purpose of this paper is the illustration of the results obtained in a research project, devoted to design an expert system assisting the programmer in-the-large in his activity of problem analysis and software design: the ESAP (Expert System for Automatic Programming) (Guida et al. (1984); Guida et al. (1985)). The environment where the ESAP has been designed refers to a new rearrangement of the softuare Life-cycLe, in which several tools for automating software production are available. We call this environment Software Factory of the Future CSFF), as illustrated in Figure 1.

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IJCAI Conference 1985 Conference Paper

Representing Procedural Knowledge in Expert Systems: An Application to Process Control

  • Massimo Gallanti
  • Giovanni Guida
  • Luca Spampinato
  • Alberto Stefanini

The paper presents a novel expert system architecture which supports explicit representation and effective use of both declarative and procedural knowledge. These two types of expert knowledge are represented by means of produc­ tion rules and event-graphs respectively, and they are pro­ cessed by a unified inference engine. Communication between the rule level and the event-graph level is based on a full visibility of each level on the internal state of the other, and it is structured in such a way as to allow each level to exert control on the other. This structure offers several advantages over more tradi­ tional architectures. Knowledge representation is more natural and transparent; knowledge acquisition turns out to be easier as pieces of knowledge can be immediately represented without the need of complex transformation and restructuring; inference is more effective due to reduced non-determinism resulting from explicit represen­ tation of fragments of procedural knowledge in eventgraphs; finally, explanations are more natural and under­ standable. The proposed architecture has been adopted for the design of PROP, an expert system for on-line monitoring of the cycle water pollution in a thermal power plant. PROP is run­ ning on a SUN-2 workstation and has been tested on a sam­ ple of real cases.

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