A comparison of sceptical NAF-free logic programming approaches

Recently there has been increased interest in logic programming-based default reasoning approaches which are not using negation-as-failure in their object language. Instead, default reasoning is modelled by rules and a priority relation among them. Historically the first logic in this class was Defeasible Logic. In this paper we will study its relationship to other approaches which also rely on the idea of using logic rules and priorities. In particular we will study sceptical LPwNF, courteous logic programs, and priority logic

On subsumption and semiunification in feature algebras

AbstractWe consider a generalization of term subsumption, or matching, to a class of mathematical structures which we call feature algebras. We show how these generalize both first-order terms and the feature structures used in computational linguistics. The notion of term subsumption generalizes to a natural notion of algebra homomorphism. In the setting of feature algebras, unification, corresponds naturally to solving constraints involving equalities between strings of unary function symbols, and semiunification also allows inequalities representing subsumption constraints. Our generalization allows us to show that the semiunification problem for finite feature algebras is undecidable. This implies that the corresponding problem for rational trees (cyclic terms) is also undecidable

Interdefinability of defeasible logic and logic programming under the well-founded semantics

We provide a method of translating theories of Nute's defeasible logic into logic programs, and a corresponding translation in the opposite direction. Under certain natural restrictions, the conclusions of defeasible theories under the ambiguity propagating defeasible logic ADL correspond to those of the well-founded semantics for normal logic programs, and so it turns out that the two formalisms are closely related. Using the same translation of logic programs into defeasible theories, the semantics for the ambiguity blocking defeasible logic NDL can be seen as indirectly providing an ambiguity blocking semantics for logic programs. We also provide antimonotone operators for both ADL and NDL, each based on the Gelfond-Lifschitz (GL) operator for logic programs. For defeasible theories without defeaters or priorities on rules, the operator for ADL corresponds to the GL operator and so can be seen as partially capturing the consequences according to ADL. Similarly, the operator for NDL captures the consequences according to NDL, though in this case no restrictions on theories apply. Both operators can be used to define stable model semantics for defeasible theories.Comment: 36 pages; To appear in Theory and Practice of Logic Programming (TPLP

Towards the Integration of Object-Oriented Constructs within Structured Query Language (SQL)

This paper explores the possibility of coupling SQL with a semantic data model. For this study, the primary objective was to build a working prototype of a program that allows a database designer to define data objects and their respective interrelationships using the Object-oriented Semantic Association Model (OSAM*). The prototype isolates from the designer the low level commands (i.e., CREATE TABLE, CREATE INDEX) which comprise the SQL data definition language (DOL). Once the objects are defined by the designer, the prototype generates the relational database table definitions without the designer having to directly use the SQL DOL

Sistema Olimpo: tecnologia da informação jurídica para o Conselho de Segurança da ONU

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de ProduçãoA tecnologia da informação jurídica baseia-se na representação do conhecimento jurídico para potencializar sistemas de recuperação de informações textuais. Com base na experiência adquirida na construção de sistemas anteriores (Digesto, Metajuris, Metalex, Themis, Prudentia e Jurisconsulto), alguns dos quais inteligentes, bem como na avaliação de serviços tecnológicos oferecidos por tribunais brasileiros, os pesquisadores do grupo de inteligencia aplicada ao direito do PPGEP aceitaram o desafio de estruturar um novo sistema para aplicação nas resoluções do Conselho de Segurança da ONU. Esta empreitada teve como produto a construção do Sistema Olimpo, cujas características serão descritas no presente trabalho, assim como seu processo de consolidação, bem como seus mecanismos de funcionamento. Sua tarefa é recuperar, de forma inteligente, as resoluções mais semelhantes ao texto oferecido como entrada

Questioning teletechnologies : a study on the notion of inheritance in Derrida

Ankara : The Department of Communicaiton and Design and the Institute of Economics and Social Sciences of Bilkent University, 2009.Thesis (Master's) -- Bilkent University, 2009.Includes bibliographical references leaves 94-95.This  study  aims  to  trace  the  perspective  on  media  and  technology  in  Jacques  Derrida’s  thought. For  this purpose, a discussion of  the notion of inheritance is  presented. This notion marks essential themes in Derrida’s approach to modern  teletechnologies.  Associations  between  the  notion  of  inheritance  and  fundamental  questions  in  the  thought  of  deconstruction  such  as  experience,  writing  and  belief  are  explored.  The  questions  that  arise  through  the  contextualization  of  modern  teletechnologies  is  put  forth  by  a  reading  of  the  philosophical  dialogue  between  Bernard  Stiegler  and  Jacques  Derrida.  It  is  argued  that  the  experience  of  bearing  witness,  to  which  Derrida  ascribes  a  constitutive role in the formation of the social bond, obtains a new context by the  expansion of teletechnologies. Berksun, FıratM.S

Parameterized type expansion in the feature structure formalism TDL

Over the last few years, unification-based grammar formalisms have become the predominant paradigm in natural language processing systems because of their monotonicity, declarativeness, and reversibility. From the viewpoint of computer science, typed feature structures can be seen as data structures that allow representation of linguistic knowledge in a uniform fashion. Type expansion is an operation that makes the constraints on a typed feature structure explicit and determines their satisfiability. We describe an efficient expansion algorithm that takes care of recursive type definitions and allows exploration of different expansion strategies through the use of control knowledge. This knowledge is specified in a separate layer, independently of grammatical information. Memoization of the type expansion function drastically reduces the number of unifications. In the second part, nonmonotonic extensions to TDL and the implementation of well-typedness checks are presented. Both are closely related to the type expansion algorithm. The algorithms have been implemented in Common Lisp and are integrated parts of TDL and a large natural language dialog system

Nonmonotonic inheritance in object-oriented deductive database languages

Deductive object-oriented frameworks integrate logic rules and inheritance. There, specific problems arise: Due to the combination of deduction and inheritance, (a) deduction can take place depending on inherited facts, thus raising indirect conflicts, and (b) also the class hierarchy and -membership is subject to deduction. From this point of view, we investigate the application of the extension sematics of Default Logic to deductive object-oriented database languages. By restricting the problem to Horn programs and a special type of defaults tailored to the semantics of inheritance, a forward-chaining construction of a Herbrand-style representation of extensions is possible. This construction is compared with a solution as implemented in the F-Logic system Florid which is based on a combination of classical deductive fixpoints and an inheritance-trigger mechanism. From the F-Logic point of view, the main contribution of the report is to investigate the relationship between inheritance-canonic models as defined in [KLW95] and classical AI frameworks: we show that the semantics which is defined and implemented for F-Logic coincides with the standard semantics of Default Logic and Inheritance Networks. In this report, we restrict ourselves to scalar methods. (orig.)Available from TIB Hannover: RR 5165(114) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman