Maurizio Martelli

Declarative modeling of the operational behavior of logic languages

Abstract The paper defines a new declarative semantics for logic programs, which is based on interpretations containing (possibly) non-ground atoms. Two different interpretations are introduced and the corresponding models are defined and compared. The classical results on the Herbrand model semantics of logic programs are shown to hold in the new models too (i.e. existence of a minimal model, fixpoint characterization, etc.). With the new models, we have a stronger soundness and completeness result for SLD-resolution. In particular, one of the two models allows the set of computed answer substitutions to be characterized precisely.

The s-semantics approach: theory and applications.

Abstract This paper is a general overview of an approach to the semantics of logic programs whose aim is to find notions of models which really capture the operational semantics, and are, therefore, useful for defining program equivalences and for semantics-based program analysis. The approach leads to the introduction of extended interpretations which are more expressive than Herbrand interpretations. The semantics in terms of extended interpretations can be obtained as a result of both an operational (top-down) and a fixpoint (bottom-up) construction. It can also be characterized from the model-theoretic viewpoint, by defining a set of extended models which contains standard Herbrand models. We discuss the original construction modeling computed answer substitutions, its compositional version, and various semantics modeling more concrete observables. We then show how the approach can be applied to several extensions of positive logic programs. We finally consider some applications, mainly in the area of semantics-based program transformation and analysis.

A model-theoretic reconstruction of the operational semantics of logic programs

Abstract In this paper we define a new notion or truth on Herbrand interpretations extended with variables which allows us to capture, by means of suitable models, various observable properties, such as the ground success set, the set of atomic consequences, and the computed answer substitutions. The notion of truth extends the classical one to account for non-ground formulas in the interpretations. The various operational semantics are all models. An ordering on interpretations is defined to overcome the problem that the intersection of a set of models is not necessarily a model. The set of interpretations with this partial order is shown to be a complete lattice, and the greatest lower bound of any set of models is shown to be a model. Thus there exists a least model, which is the least Herbrand model and therefore the ground success set semantics. Richer operational semantics are non-least models, which can, however, be effectively defined by fixpoint constructions. The model corresponding to the computed answer substitutions operational semantics is the most primitive one (the others can easily be obtained from it).

Logic-based specification languages for intelligent software agents

The research field of Agent-Oriented Software Engineering (AOSE) aims to find abstractions, languages, methodologies and toolkits for modeling, verifying, validating and prototyping complex applications conceptualized as Multiagent Systems (MASs). A very lively research sub-field studies how formal methods can be used for AOSE. This paper presents a detailed survey of six logic-based executable agent specification languages that have been chosen for their potential to be integrated in our ARPEGGIO project, an open framework for specifying and prototyping a MAS. The six languages are

Integrity constraints in logic databases

\textsf{ConGolog}

An agent-based framework for sketched symbol interpretation

,

Customizing AOSE methodologies by reusing AOSE features

\textsf{AGENT-0}

Transactions and updates in deductive databases

, the

Strict completion of logic programs

\textsf{IMPACT}

Model checking linear logic specifications

agent programming language,