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Observational structures and their logic
No full textAbstractA poweful paradigm is presented for defining semantics of data types which can assign sensible semantics also to data representing processes. Processes are abstractly viewed as elements of observable sort in an algebraic structure, independently of the language used for their description. In order to define process semantics depending on the observations we introduce observational structures, essentially first-order structures where we specify how processes are observed. Processes are observationally related by means of experiments considered similar depending on a similarity law and relations over processes are propagated to relations over elements of non-observable sort by a propagation law. Thus an observational equivalence is defined, as union of all observational relations, which can be seen as a very abstract generalization of bisimulation equivalences introduced by David Park.Though being general and abstract our construction allows to extend and improve interesting classical results. For example it is shown that for finitely observable structures the observational equivalence is obtainable as a limit of a denumerable chain of iterations; our conditions, which apply to algebraic structures in general, when instantiated in the case of labelled transition systems, are more liberal than the finitely branching condition. More importantly, we show how to associate with an observational structure various modal observational logics, related to sets of experiment schemas, that we call pattern sets. The main result of the paper proves that for any family of pattern sets representing the simulation law the corresponding modal observational logic is a Hennessy—Milner logic: two observable objects are observationally equivalent if and only if they satisfy the same set of modal observational formulas. Indeed observational logics generalize to first-order structures various modal logics for labelled transition systems. Applications are shown to multilevel parallelism, higher-order concurrent calculi, distributed and branching bisimulation.The theory presented in the paper is not at all confined to give semantics of processes. Indeed it provides a general semantic paradigm for abstract data type specifications, where some data are processes. In order to support this claim, in the final section we briefly consider algebraic specifications and give small examples of specifications integrating processes, data types and functions
An Integrated Algebraic Approach to the Specification of Data Types, Processes and Objects
No full text
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
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