1,721,047 research outputs found
Neubot: A Software Tool Performing Distributed Network Measurements to Increase Network Transparency
No full textWe present Neubot (the network neutrality bot), a network-measurement platform designed to run network-performance experiments from the network edges. The data produced by Neubot is useful to increase network transparency and to study network neutrality. We describe the Neubot architecture (based on plugins that emulate several protocols and are able to run client-server and peer-to-peer tests), which is one of the main contributions of this thesis. We describe the current Neubot implementation (Neubot 0.4.16.9), we provide up-to-date data concerning Neubot deployment, and we show how we used Neubot to run four diverse large-scale measurements campaigns involving more than 1,000 Neubot instances each. Such measurements campaign, which were only possible because the Neubot architecture was already flexible enough to allow us to deploy new network experiments on the already installed Neubot instances, were concerned with, respectively: the measurement of broadband speed using the HTTP protocol; the study of the link between application-level measurements and the packet-loss rate experienced by TCP (which is the other main contribution of this thesis); the study of rate adaptation algorithms for the dynamic adaptive streaming over HTTP streaming technology (DASH); emulating the BitTorrent protocol. We conclude the thesis with the description of Neuviz (the Neubot visualizer), a prototype data-visualization architecture that loads Neubot data and allows to navigate the data looking for potential deviations from network neutrality. Despite being still in beta stage, Neuviz already allowed to spot three anomalies in the median speeds measured by the Neubot `HTTP Speedtest' and BitTorrent test
Collaborative Open Data versioning: a pragmatic approach using Linked Data
Full text linkMost Open Government Data initiatives are centralised and unidirectional (i.e., they release data dumps in CSV or PDF format). Hence for non trivial applications reusers make copies of the government datasets to curate their local data copy. This situation is not optimal as it leads to duplication of efforts and reduces the possibility of sharing improvements. To improve the usefulness of publishing open data, several authors recommeded to use standard formats and data versioning. Here we focus on publishing versioned open linked data (i.e., in RDF format) because they allow one party to annotate data released independently by another party thus reducing the need to duplicate entire datasets. After describing a pipeline to open up legacy-databases data in RDF format, we argue that RDF is suitable to implement a scalable feedback channel, and we investigate what steps are needed to implement a distributed RDFversioning system in productio
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
Is there such a thing as free government data?
Full text linkThe recently-amended European Public Sector Information (PSI) Directive rests on the assumption that government data is a valuable input for the knowledge economy. As a default principle, the directive sets marginal costs as an upper bound for charging PSI. This article discusses the terms under which the 2013 consultation on the implementation of the PSI Directive addresses the calculation criteria for marginal costs, which are complex to define, especially for internet-based services. What is found is that the allowed answers of the consultation indirectly lead the responder to reason in terms of the average incremental cost of allowing reuse, instead of the marginal cost of reproduction, provision and dissemination. Moreover, marginal-cost pricing (or zero pricing) is expected to lead to economically efficient results, while aiming at recouping the average incremental cost of allowing re-use may lead to excessive fees
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
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