1,720,966 research outputs found
Axiomatic and logical characterizations of probabilistic preorders and trace semantics
No full textnon disponibileRandomization was first introduced in computer science in order to improve the
efficiency of several problems that were classified unfeasible or particularly inefficient, by giving algorithms the ability to flip coins, that is, of making probabilistic
choices at some point of the computation. In the paper Probabilistic Algorithms, Rabin proposed efficient solutions to the problems of determining the nearest
neighbor and to state the primality of a given number, for which there were no
efficient non-probabilistic solutions. Later, he applied probability to a problem of
distributed computing, which was not feasible without the use of randomiza-
tion. On the base of these important results, a large set of problems were solved
with the use of probabilistic choices in the computation, and a wide range
of applications and modelings were proposed in the framework of concurrency
theory.
However, together with probabilistic behaviors, in the modeling and verification of concurrent processes it is crucial to take into account the presence of
a phenomenon called nondeterminism. In general, nondeterminism is a way to
model the lack of knowledge about the relative speeds of two or more processes
running in parallel, as it may not be possible to determine which of the processes
is performing the next action. On the other hand, there are further circumstances
in which nondeterminism arises and must be modeled in order to obtain a correct description of the possible behaviors of a process. In particular, the external
choices made by the environment in order to condition the execution of a process
are modeled as nondeterministic choices, since the decisions taken by a user or by
a malicious entity may not be predictable a priori by the system. Furthermore,
since a semantic model of a process can be seen as a specification of the process,
the introduction of nondeterministic choices in the model may reflect the ability
to implement the specification by choosing one of the possible alternatives given,
all leading to consistent implementations. The kinds of nondeterministic behaviors described can be all referred to as pure nondeterminism, in contrast with the
probabilistic nondeterminism, which models the fact that events are governed by
probability distributions
Axiomatization of Trace Semantics for Stochastic Nondeterministic Processes
No full textWe give a complete axiomatization of trace distribution precongruence for probabilistic nondeterministic processes based on a process algebra that includes internal behavior and recursion. The axiomatization is given for two different semantics of the process algebra that are consistent with the alternating model of Hansson and the non-alternating model of Segala, respectively. It is shown that the two semantics coincide up to trace distribution precongruence
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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