Building and Combining Matching Algorithms

International audienceThe concept of matching is ubiquitous in declarative programming and in automated reasoning. For instance, it is a key mechanism to run rule-based programs and to simplify clauses generated by theorem provers. A matching problem can be seen as a particular conjunction of equations where each equation has a ground side. We give an overview of techniques that can be applied to build and combine matching algorithms. First, we survey mutation-based techniques as a way to build a generic matching algorithm for a large class of equational theories. Second, combination techniques are introduced to get combined matching algorithms for disjoint unions of theories. Then we show how these combination algorithms can be extended to handle non-disjoint unions of theories sharing only constructors. These extensions are possible if an appropriate notion of normal form is computable

ASF+SDF Parsing Tools Applied to ELAN

This paper describes the development of a new ELAN parser using Asf+Sdf parsing technology. Asf+Sdf and ELAN are two modern rule-based systems. Both systems have their own features and application domains, however, both formalism have user-dened syntax for dening rewrite rules. The Asf+Sdf Meta-Environment uses powerful and ecient generic parsing tools, whereas the ELAN parser is based on an Earley parser. Furthermore, the ELAN syntax is \hard-wired" in the parser, which makes adaptations of the syntax cumbersome. The use of Asf+Sdf parsing technology makes the ELAN syntax more open and adaptable, however, some features of the ELAN syntax makes the development of a parser a challenging problem. 1998 ACM Computing Classication System: D.2.6, D.3.1, D.3.4, F.4.2 Keywords and Phrases: parsing, rewriting systems, language denition, intermediate format Note: To appear in Proceedings of Third International Workshop on Rewriting Logic and its Applications (WRLA'2000), 2000 Not..

Propriétés optiques déduites du spectre de réflexion de CuI à basse température

The reflection spectrum on a CuI bulk crystal has been studied at low temperatures and the absorption spectrum has been deduced by means of a Kramers-Krönig analysis. Approximate values of the oscillator strengths f have been calculated. They are in qualitative agreement with first class excitonic transitions. Three excitonic levels have been observed with holes formed in the Γ8 band and two with holes from Γ7. The n = 1 level of Γ8 shows a fine structure which can be explained in the JJ coupling scheme. As in CuCl and CuBr, a very weak absorption peak of CuI can be assigned to a transition accompanied by a longitudinal phonon. On the higher energy side, transitions due to deeper bands have been observed. These transitions have been interpreted by extrapolation from a CuCl band scheme.Le spectre de réflexion d'un cristal massif de CuI a été étudié aux basses températures. Le spectre d'absorption en a été déduit par une analyse de Kramers-Krönig. Un ordre de grandeur des facteurs f, en accord qualitatif avec des transitions excitoniques de première classe, a été obtenu. On observe trois niveaux excitoniques formés avec les trous de la bande Γ8 et deux avec des trous de Γ 7. Le niveau n = 1 de Γ8 présente une structure fine qui peut être expliquée dans le couplage JJ et, par analogie avec CuCl et CuBr, un très faible maximum d'absorption peut être attribué à une transition assistée d'un phonon longitudinal. Du côté des plus grandes énergies, on a observé trois transitions liées à des bandes plus profondes. Ces transitions s'interprètent en première approximation à partir d'un schéma de bandes extrapolé à partir de CuCl

Decision Procedures for the Formal Analysis of Software

Catching bugs in programs is difficult and time-consuming. The effort of debugging and proving correct even small units of code can surpass the effort of programming. Bugs inserted while “programming in the small” can have dramatic consequences for the consistency of a whole software system as shown, e.g., by viruses which can spread by exploiting buffer overflows, a bug which typically arises while coding a small portion of code. To detect this kind of errors, many verification techniques have been put forward such as static analysis and model checking

ÉTUDE DES RAIES EXCITONIQUES STIMULÉES DANS UN CHAMP MAGNÉTIQUE DANS CuCl A 4,2 °K

L'absorption et la luminescence de cristaux de CuCl, à la température de 4,2 °K, présentent une raie commune (ν1 = 25 814 cm-1, λ1 = 3 873,7 Å), très fine, dont l'intensité est stimulée par un champ magnétique. L'intensité d'oscillateur de cette raie a été mesurée dans un champ de 33 kG ; f ~ 10-6, ainsi que la variation du coefficient d'absorption maximum Km en fonction de l'intensité du champ magnétique. L'origine de cette raie est discutée. Elle correspond peut-être à une transition excitonique interdite J = 0 → J = 0 ou J = 0 → J = 2.In the absorption and emission spectra of CuCl crystals, the very weak line (ν1 = 25 814 cm-1, λ1 = 3 873.7 Å) is observed at low temperature. A magnetic field produces an increase of the intensity of this line. The oscillator strengh in a field of 33 kG (f ~ 10-6) and the variation of the absorption coefficient with respect to the intensity of the magnetic field has been measured. This line corresponds probably to a forbidden excitonic transition between a ground state J = 0 and a state J = 0 or J = 2