Abduction in Well-Founded Semantics and Generalized Stable Models

Abductive logic programming offers a formalism to declaratively express and solve problems in areas such as diagnosis, planning, belief revision and hypothetical reasoning. Tabled logic programming offers a computational mechanism that provides a level of declarativity superior to that of Prolog, and which has supported successful applications in fields such as parsing, program analysis, and model checking. In this paper we show how to use tabled logic programming to evaluate queries to abductive frameworks with integrity constraints when these frameworks contain both default and explicit negation. The result is the ability to compute abduction over well-founded semantics with explicit negation and answer sets. Our approach consists of a transformation and an evaluation method. The transformation adjoins to each objective literal $O$ in a program, an objective literal $not(O)$ along with rules that ensure that $not(O)$ will be true if and only if $O$ is false. We call the resulting program a {\em dual} program. The evaluation method, \wfsmeth, then operates on the dual program. \wfsmeth{} is sound and complete for evaluating queries to abductive frameworks whose entailment method is based on either the well-founded semantics with explicit negation, or on answer sets. Further, \wfsmeth{} is asymptotically as efficient as any known method for either class of problems. In addition, when abduction is not desired, \wfsmeth{} operating on a dual program provides a novel tabling method for evaluating queries to ground extended programs whose complexity and termination properties are similar to those of the best tabling methods for the well-founded semantics. A publicly available meta-interpreter has been developed for \wfsmeth{} using the XSB system.Comment: 48 pages; To appear in Theory and Practice in Logic Programmin

Preferential theory revision

AbstractEmploying a logic program approach, this paper focuses on applying preferential reasoning to theory revision, both by means of preferences among existing theory rules, and by means of preferences on the possible abductive extensions to the theory. And, in particular, how to prefer among plausible abductive explanations justifying observations

Eye gaze in individuals with and without convergence insufficiency

Aims of the study: Characterization of the eye gaze, through the analysis of eye movements during fixation and pursuit of a target in young adults with convergence insufficiency and young adults with normal binocular vision. In the horizontal from left-right in the vertical from up-down, for the most used direction, in the horizontal from right-left, and in the vertical from down-up for the less used direction.info:eu-repo/semantics/publishedVersio

Cibercultura, Simbiose e Sincretismo

O impacto da Cibercultura, dos dispositivos digitais nos jovens enquanto extensões do seu corpo, pode ser visto em termos do decréscimo da estruturação de pensamento e informação, acréscimo da impulsividade na perceção e ação, e no desenvolvimento de mecanismos de defesa mais primitivos. Estes impactos adversos resultam num sentimento de isolamento e desvalorização, em frustração no presente e incerteza no futuro, em exteriorização e identidades flutuantes, nas identificações miméticas e adesivas, em menor coesão do self, e numa diminuída tolerância ao outro. Este artigo foca os seguintes temas: (1) Simbiose versus Sincretismo: As afirmações da Simbiose. As diluições do Sincretismo; (2) Súmula: Sincretismo a mais, simbiose a menos. Falta de uma maior co-construção do conhecimento, duradoura e sustentável. Falta de maior e mais independente aprofundamento cognitivo pessoal. Falta de capacidade para estar só; (3) Causalidade e Livre Arbítrio: Causalidade simbiótica versus sincrética; (4) Coda: Cyber-selfs distribuídos ou não

Prolegómeno a uma neurologia artificial

Exploram-se algumas potencialidades de aproximação entre a neurologia e as ciências da computação, com particular ênfase na distinção hardware/software e suas consequências. ------ ABSTRACT ------ Potential bridging points between neurology and computer science are explored, with special emphasis on the hardware7software distinction and its consequences

Binocular vision and balance measurement and analysis

An individual's ability to see and function visually is determined largely by the relative contributions of a number of underlying components of vision designated as visual abilities. These visual abilities are: acuity, visual field, motility, brain functions, and light and colour reception others consider also contrast, accommodation, and binocular vision. The efficacy of our visual system influences the way we collect and process information. It is through the conjugated movement of the two eyes that we can fix and pursue one object. The ocular movements and the binocular vision are linked and they are influenced mutually. The measurement device most often used for measuring eye movements is commonly known as an eye tracker. In order to characterize the mechanisms of fixation and persecution and the way how binocular vision influences them, we use in our study the Eye Tracking System-ASL 504, because allows an evaluation next to the natural conditions. Our sample was composed by young adults, distributed in two groups, one formed by individuals with normal binocular vision evaluated in two different conditions (binocular and monocular) and another one by individuals with convergence insufficiency, both with 24 participants. The individuals observe a small target, moving in four directions (left-right; right-left; up-down; down-up). The selected variables were: the mean duration of the fixation and mean saccadic amplitudes. The study of normality seems to indicate that the Eye Tracker is an efficient system for the study of ocular movements (fixation and pursuit). The eye-tracking system that we use showed good discrimination for the selected variables. We think that this study shows the important contribution that eye tracking can give in the analysis, of the functional alterations of binocular vision because allows us to evaluate them in conditions very next to reality.info:eu-repo/semantics/publishedVersio