1,720,962 research outputs found
Formalisation of asynchronous interactions
No full textLarge computing systems are generally built by connecting several distributed subsystems. The way these entities communicate is crucial to the proper functioning of the overall composed system. An in-depth study of these interactions makes sense in the context of the formal development and verification of such systems. The interactions fall in two categories: synchronous and asynchronous communication. In synchronous communication, the transmission of a piece of information - the message - is instantaneous. Asynchronous communication, on the other hand, splits the transmission in a send operation and a receive operation. This make the interleaving of other events possible and lead to new behaviours that may or may not be desirable. The asynchronous world is often viewed as a monolithic counterpart of the synchronous world. It actually comes in multiple models that provide a wide range of properties that can be studied and compared. This thesis focuses on communication models that order the delivery of messages: for instance, the "FIFO" models ensure that some messages are received in the order of their emission. We consider classic communication models from the literature as well as a few variations. We highlight the differences that are sometimes overlooked. First, we propose an abstract, logical, and homogeneous formalisation of the communication models and we establish a hierarchy that extends existing results. Second, we provide an operational approach with a tool that verifies the compatibility of compositions of peers. We mechanise this tool with the TLA+ specification language and its model checker TLC. The tool is designed in a modular fashion: the commmunicating peers, the temporal compatibility properties, and the communication models are specified independently. We rely on a set of uniform operational specifications of the communication models that are based on the concept of message history. We identify and prove the conditions under which they conform to the logical definitions and thus show the tool is trustworthy. Third, we consider concrete specifications of the communication models that are often found in the literature. Thus, the models are classified in terms of ordering properties and according to the level of abstraction of the different specifications. The concept of refinement covers these two aspects. Thus, we model asynchronous point-to-point communication along several levels of refinement and then, with the Event-B method, we establish and prove all the refinements between the communication models and the alternative specifications of each given model. This work results in a detailed map one can use to develop a new model or find the one that best fits given needs. Eventually we explore ways to extend our work to multicast communication that consists in sending messages to several recipients at once. In particular, we highlight the differences in the hierarchy of the models and how we modify our verification tool to handle this communication paradigm
Formalisation des interactions asynchrones
No full textLes systèmes informatiques sont construits par composition de plusieurs sous-systèmes répartis. La manière dont communiquent ces entités, ou pairs, joue un rôle clé dans la bonne marche du système composé. L'étude détaillée de ces interactions est donc essentielle dans le cadre de la vérification et du développement formel de tels systèmes. Ces interactions se décomposent en deux catégories: la communication synchrone et la communication asynchrone. La communication synchrone admet une transmission instantanée de l'information, le message, entre deux entités. La communication asynchrone, en revanche, prend en compte le découplage de la transmission du message en une opération d'envoi puis de réception avec la possibilité que des événements s'intercalent entre les deux donnant ainsi lieu à des variations de comportement, désirables ou non, des systèmes. Souvent considérée comme une entité monolithique duale du monde synchrone, le monde asynchrone se décline en réalité en de multiples modèles qui peuvent induire sur la communication une grande variété de propriétés qu'il convient de caractériser et comparer. Cette thèse se focalise sur les modèles de communication qui orchestrent l'ordre de délivrance des messages : par exemple les modèles dits FIFO qui assurent que certains messages sont reçus dans l'ordre dans lequel ils ont été émis. Nous considérons des modèles de communication classiques de la littérature ainsi que des variations de ces modèles dont nous explicitons les différences parfois négligées. Dans un premier temps nous proposons une formalisation logique abstraite et homogène des modèles de communication considérés et nous les hiérarchisons en étendant des résultats existants. Nous proposons dans un second temps une approche opérationnelle sous forme d'un outil de vérification de compositions de pairs que nous mécanisons à l'aide du langage de spécification TLA+ et du vérificateur de modèles TLC. Cet outil permet de spécifier des pairs communicants et des propriétés temporelles à vérifier pour les différents modèles de communication de façon modulaire. Pour cela, nous apportons un ensemble de spécifications uniformes et opérationnelles des modèles de communication basé sur la notion d'histoires de messages. Nous identifions et prouvons les conditions de leur conformité aux définitions logiques et validons ainsi la pertinence de notre outil. Dans un troisième temps nous considérons des spécifications concrètes de nos modèles de communication, semblables à nombre de celles présentes dans la littérature. Nous disposons donc d'une hiérarchisation des modèles selon les propriétés d'ordre qu'ils garantissent mais également d'une autre hiérarchisation pour un modèle donné entre sa définition logique abstraite et ses implantations concrètes. Ces deux dimensions correspondent à deux dimensions du raffinement. Nous introduisons graduellement par raffinement la notion de communication asynchrone point à point et prouvons, grâce à la méthode Event-B, tous les liens de raffinement entre les différents modèles de communication et leurs déclinaisons. Nous offrons ainsi une cartographie détaillée des modèles pouvant être utilisée pour en développer de nouveaux ou identifier les modèles les plus adaptés à des besoins donnés. Enfin, nous proposons des pistes d'extension de nos travaux à la communication par diffusion où un message peut être envoyé simultanément à plusieurs destinataires. En particulier, nous montrons les différences induites dans la hiérarchie des modèles et les adaptations à effectuer sur notre outil de vérification pour prendre en compte ce mode de communicationLarge computing systems are generally built by connecting several distributed subsystems. The way these entities communicate is crucial to the proper functioning of the overall composed system. An in-depth study of these interactions makes sense in the context of the formal development and verification of such systems. The interactions fall in two categories: synchronous and asynchronous communication. In synchronous communication, the transmission of a piece of information - the message - is instantaneous. Asynchronous communication, on the other hand, splits the transmission in a send operation and a receive operation. This make the interleaving of other events possible and lead to new behaviours that may or may not be desirable. The asynchronous world is often viewed as a monolithic counterpart of the synchronous world. It actually comes in multiple models that provide a wide range of properties that can be studied and compared. This thesis focuses on communication models that order the delivery of messages: for instance, the "FIFO" models ensure that some messages are received in the order of their emission. We consider classic communication models from the literature as well as a few variations. We highlight the differences that are sometimes overlooked. First, we propose an abstract, logical, and homogeneous formalisation of the communication models and we establish a hierarchy that extends existing results. Second, we provide an operational approach with a tool that verifies the compatibility of compositions of peers. We mechanise this tool with the TLA+ specification language and its model checker TLC. The tool is designed in a modular fashion: the commmunicating peers, the temporal compatibility properties, and the communication models are specified independently. We rely on a set of uniform operational specifications of the communication models that are based on the concept of message history. We identify and prove the conditions under which they conform to the logical definitions and thus show the tool is trustworthy. Third, we consider concrete specifications of the communication models that are often found in the literature. Thus, the models are classified in terms of ordering properties and according to the level of abstraction of the different specifications. The concept of refinement covers these two aspects. Thus, we model asynchronous point-to-point communication along several levels of refinement and then, with the Event-B method, we establish and prove all the refinements between the communication models and the alternative specifications of each given model. This work results in a detailed map one can use to develop a new model or find the one that best fits given needs. Eventually we explore ways to extend our work to multicast communication that consists in sending messages to several recipients at once. In particular, we highlight the differences in the hierarchy of the models and how we modify our verification tool to handle this communication paradigm
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
No full textWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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