Disjunctive Logic Programs with Inheritance

The paper proposes a new knowledge representation language, called DLP<, which extends disjunctive logic programming (with strong negation) by inheritance. The addition of inheritance enhances the knowledge modeling features of the language providing a natural representation of default reasoning with exceptions. A declarative model-theoretic semantics of DLP< is provided, which is shown to generalize the Answer Set Semantics of disjunctive logic programs. The knowledge modeling features of the language are illustrated by encoding classical nonmonotonic problems in DLP<. The complexity of DLP< is analyzed, proving that inheritance does not cause any computational overhead, as reasoning in DLP< has exactly the same complexity as reasoning in disjunctive logic programming. This is confirmed by the existence of an efficient translation from DLP< to plain disjunctive logic programming. Using this translation, an advanced KR system supporting the DLP< language has been implemented on top of the DLV system and has subsequently been integrated into DLV.Comment: 28 pages; will be published in Theory and Practice of Logic Programmin

Magnetic Intensification of the Li I λ6708 Line and the Abundance and Age Spread in Young Cool Stars

The lithium abundance is considered the best age indicator of young cool stars and its spread is fundamental for the understanding of star formation mechanisms, in particular, of possible multiple formation events within a single region. The observed spread in the equivalent widths of lithium lines cannot be understood on the basis of present stellar evolutionary models, and proposed explanations invoke stellar activity. Despite the fact that magnetic fields of several tenths of a tesla are expected theoretically and are observed in these stars, their effect on the formation of spectral lines has always been neglected. In this Letter, the possibility that the magnetic intensification of spectral lines results in an overestimation of lithium abundances is quantitatively explored through the computation of Stokes I profiles of the Li I λ6708 doublet, using the polarized line synthesis code COSSAM. Spectral synthesis for fields up to 1 T reveals the doublet to be sensitive to magnetic fields, with equivalent widths up to 60% larger than the zero field value and a possible overestimation of lithium abundances by 1 dex. Consequently, the contribution of magnetic fields to the lithium spread appears to be significant. Neglecting the magnetic intensification of the Li I λ6708 doublet could make stars appear millions of years younger and make stellar formation mechanisms appear to last much longer than usually supposed. To conclude, for lithium abundance determinations and estimates of lithium based stellar ages, one has to obtain magnetic field measurements and to include them in the spectrum analysis

Industrial Poles and Local Development: a Survey on Food Technologies in the Mezzogiorno of Italy

This paper presents the results of an empirical survey carried out by Ceris-Cnr on the food-process machines industry in the South of Italy (Mezzogiorno).This survey has highlighted that in the southern regions, although the presence of important agroindustrial poles, the food-technology industry is characterized by the presence of a limited number of small enterprises with a craftmade organization. Nevertheless these SMEs are interested in introducing new innovative technologies.This situation of technological and organizational constraints derives by: an industrial policy that has not encouraged the development of the existing small enterprises; lackness of specialized technicians and workers; difficult relationships between enterprise and credit system; scarce cooperative relations between enterprises and research institutes.In order to improve the organization of the southern enterprises it would be necessary to activate instruments of industrial policy aimed to improve industrial infrastructures and create service companies supporting the enterprises operations on new markets.

Una Notte in Napoli : A Night in Naples

https://digitalcommons.library.umaine.edu/mmb-ps/1845/thumbnail.jp