1,720,956 research outputs found
2-CATEGORIA E TEORIA DA PROVA
No full textDedução Natural para a lógica intuicionista tem sido relacionada à Teoria das Categorias através do que agora é conhecido por Lógica Categórica. Essa relação é fortemente baseada no isomorfismo de Curry-Howard entre Dedução Natural e (lambda)-Cálculo Tipado. Esta dissertação descreve alguns aspectos dessa relação com o objetivo de propor uma visão 2-categórica da Lógica Categórica. Mostramos que mesmo numa visão 2-cateórica algumas desvantagens conhecidas na Teoria das Categorias continuam valendo. Concluímos essa dissertação discutindo as vantagens de uma visão 2-categórica a partir de premissas mais fracas.Natural Deduction for intuitionistic logic has been related to Category Theory by what now is known as Categorical Logic. This relationship is strongly based on the Curry-Howard Isomorphism between Natural Deduction and typed (lambda)-Calculus. This dissertation describes some aspects of these relationship with the aim of proposing a 2-categorical view of categorical logic. We show that even under this 2-categorical view some of the drawbacks already known in ordinary Category Theory remain holding. We conclude this dissertation discussing the advantages of 2-categorical view under some weaker assumptions
ALGUMAS RELAÇÕES ENTRE CÁLCULO DE SEQUENTES E DEDUÇÃO NATURAL
No full textSegerberg apresentou uma prova geral da completude para lógicas
proposicionais. Para tal, um sistema de dedução foi definido de forma que suas
regras sejam regras para um operador booleano arbitrário para uma dada lógica
proposicional. Cada regra desse sistema corresponde a uma linha na tabela de
verdade desse operador. Na primeira parte desse trabalho, mostramos uma
extensão da ideia de Segerberg para lógicas proposicionais finito-valoradas e
para lógicas não-determinísticas. Mantemos a ideia de definir um sistema de
dedução cujas regras correspondam a linhas de tabelas verdade, mas ao invés de
termos um tipo de regra para cada valor de verdade da lógica correspondente,
usamos uma representação bivalente que usa a técnica de fórmulas separadoras
definidas por Carlos Caleiro e João Marcos. O sistema definido possui tantas
regras que pode ser difícil trabalhar com elas. Acreditamos que um sistema
de cálculo de sequentes definido de forma análoga poderia ser mais intuitivo.
Motivados por essa observação, a segunda parte dessa tese é dedicada à
definição de uma tradução entre cálculo de sequentes e dedução natural, onde
procuramos definir uma bijeção melhor do que as já existentes.Segerberg presented a general completeness proof for propositional logics.
For this purpose, a Natural Deduction system was defined in a way that its rules
were rules for an arbitrary boolean operator in a given propositional logic. Each
of those rules corresponds to a row on the operator s truth-table. In the first
part of this thesis we extend Segerbergs idea to finite-valued propositional logic
and to non-deterministic logic. We maintain the idea of defining a deductive
system whose rules correspond to rows of truth-tables, but instead of having
n types of rules (one for each truth-value), we use a bivalent representation
that makes use of the technique of separating formulas as defined by Carlos
Caleiro and João Marcos. The system defined has so many rules it might be
laborious to work with it. We believe that a sequent calculus system defined in
a similar way would be more intuitive. Motivated by this observation, in the
second part of this thesis we work out translations between Sequent Calculus
and Natural Deduction, searching for a better bijective relationship than those
already existing
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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