On the Intrinsic Locality Properties of Web Reference Streams

There has been considerable work done in the study of Web reference streams: sequences of requests for Web objects. In particular, many studies have looked at the locality properties of such streams, because of the impact of locality on the design and performance of caching and prefetching systems. However, a general framework for understanding why reference streams exhibit given locality properties has not yet emerged. In this work we take a first step in this direction, based on viewing the Web as a set of reference streams that are transformed by Web components (clients, servers, and intermediaries). We propose a graph-based framework for describing this collection of streams and components. We identify three basic stream transformations that occur at nodes of the graph: aggregation, disaggregation and filtering, and we show how these transformations can be used to abstract the effects of different Web components on their associated reference streams. This view allows a structured approach to the analysis of why reference streams show given properties at different points in the Web. Applying this approach to the study of locality requires good metrics for locality. These metrics must meet three criteria: 1) they must accurately capture temporal locality; 2) they must be independent of trace artifacts such as trace length; and 3) they must not involve manual procedures or model-based assumptions. We describe two metrics meeting these criteria that each capture a different kind of temporal locality in reference streams. The popularity component of temporal locality is captured by entropy, while the correlation component is captured by interreference coefficient of variation. We argue that these metrics are more natural and more useful than previously proposed metrics for temporal locality. We use this framework to analyze a diverse set of Web reference traces. We find that this framework can shed light on how and why locality properties vary across different locations in the Web topology. For example, we find that filtering and aggregation have opposing effects on the popularity component of the temporal locality, which helps to explain why multilevel caching can be effective in the Web. Furthermore, we find that all transformations tend to diminish the correlation component of temporal locality, which has implications for the utility of different cache replacement policies at different points in the Web.National Science Foundation (ANI-9986397, ANI-0095988); CNPq-Brazi

Characterizing Attention Cascades in WhatsApp Groups

An important political and social phenomena discussed in several countries, like India and Brazil, is the use of WhatsApp to spread false or misleading content. However, little is known about the information dissemination process in WhatsApp groups. Attention affects the dissemination of information in WhatsApp groups, determining what topics or subjects are more attractive to participants of a group. In this paper, we characterize and analyze how attention propagates among the participants of a WhatsApp group. An attention cascade begins when a user asserts a topic in a message to the group, which could include written text, photos, or links to articles online. Others then propagate the information by responding to it. We analyzed attention cascades in more than 1.7 million messages posted in 120 groups over one year. Our analysis focused on the structural and temporal evolution of attention cascades as well as on the behavior of users that participate in them. We found specific characteristics in cascades associated with groups that discuss political subjects and false information. For instance, we observe that cascades with false information tend to be deeper, reach more users, and last longer in political groups than in non-political groups.Comment: Accepted as a full paper at the 11th International ACM Web Science Conference (WebSci 2019). Please cite the WebSci versio

O monumento gótico como suporte da prática artística contemporânea

A presente investigação de tese de mestrado em gestão cultural tem como objetivo propor um projeto de intervenção contemporânea no Mosteiro de Santa Maria da Vitória – Batalha, onde realizei o meu estágio. O contexto arquitetónico, espacial, cultural e social como suporte da prática artística, assim como a consciência e tentativa de criação de intimidade entre um monumento gótico e um objeto artístico contemporâneo são o fio condutor deste projeto. Também tem a intenção de entender qual a importância deste género de projetos no património e na sua gestão e dinamização. Enquanto projeto, foi proposto a dois artistas plásticos contemporâneos a conceção de uma instalação artística através de uma abordagem ao lugar no seu contexto arquitetónico, histórico e também social: a perceção do espaço, assim como a desmistificação da experiência dos artistas no monumento surgem como a ilustração que inicia a proposta prática deste projeto. Desta forma, procuro o envolvimento de profissionais da gestão cultural, e das artes plásticas num processo colaborativo em que cada saber é operacionalizado dialogicamente. O Mosteiro da Batalha ganha um carater de instalação experimental relevando diferentes fazeres num todo definido coletivamente; o espetador torna-se parte integrante da obra. A experiência sensorial dos artistas no Mosteiro da Batalha é a base de todo o desenvolvimento do processo construtivo da obra, no final pretende-se criar um diálogo entre o monumento e a arte contemporânea, respeitando-se mutuamente. Com o tema O monumento gótico como suporte da prática artística contemporânea pretende-se desenvolver um estudo em especial sobre o Mosteiro de Santa Maria da Vitória e intervenções site-specific nesse contexto espacial em duas perspetivas, de um lado do artista e do outro da gestão do património. Será também uma reflexão acerca da arte contemporânea como expoente simbólico do lugar

A Geographical Analysis of Knowledge Production in Computer Science

We analyze knowledge production in Computer Science by means of coauthorship networks. For this, we consider 30 graduate programs of different regions of the world, being 8 programs in Brazil, 16 in North America (3 in Canada and 13 in the United States), and 6 in Europe (2 in France, 1 in Switzerland and 3 in the United Kingdom). We use a dataset that consists of 176,537 authors and 352,766 publication entries distributed among 2,176 publication venues. The results obtained for different metrics of collaboration social networks indicate the process of knowledge production has changed differently for each region. Research is increasingly done in teams across different fields of Computer Science. The size of the giant component indicates the existence of isolated collaboration groups in the European network, contrasting to the degree of connectivity found in the Brazilian and North-American counterparts. We also analyzed the temporal evolution of the social networks representing the three regions. The number of authors per paper experienced an increase in a time span of 12 years. We observe that the number of collaborations between authors grows faster than the number of authors, benefiting from the existing network structure. The temporal evolution shows differences between well-established fields, such as Databases and Computer Architecture, and emerging fields, like Bioinformatics and Geoinformatics. The patterns of collaboration analyzed in this paper contribute to an overall understanding of Computer Science research in different geographical regions that could not be achieved without the use of complex networks and a large publication database

Patterns of Mycobacterium tuberculosis-complex excretion and characterization of super-shedders in naturally-infected wild boar and red deer

Wild boar (Sus scrofa) and red deer (Cervus elaphus) are the main maintenance hosts for bovine tuberculosis (bTB) in continental Europe. Understanding Mycobacterium tuberculosis complex (MTC) excretion routes is crucial to define strategies to control bTB in free-ranging populations, nevertheless available information is scarce. Aiming at filling this gap, four different MTC excretion routes (oronasal, bronchial-alveolar, fecal and urinary) were investigated by molecular methods in naturally infected hunter-harvested wild boar and red deer. In addition MTC concentrations were estimated by the Most Probable Number method. MTC DNA was amplified in all types of excretion routes. MTC DNA was amplified in at least one excretion route from 83.0% (CI95 70.8-90.8) of wild ungulates with bTB-like lesions. Oronasal or bronchial-alveolar shedding were detected with higher frequency than fecal shedding (p 10(3) CFU/g or mL (referred here as super-shedders). Red deer have a significantly higher risk of being super-shedders compared to wild boar (OR = 11.8, CI95 2.3-60.2). The existence of super-shedders among the naturally infected population of wild boar and red deer is thus reported here for the first time and MTC DNA concentrations greater than the minimum infective doses were estimated in excretion samples from both species.We are grateful to all owners, hunters and hunting organizations that helped us to collect samples. Thanks are also due to Monica Cunha (INIAV, Portugal) for her advice during the setup of the laboratorial diagnosis techniques. Nuno Santos was supported by the Fundacao para a Ciencia e a Tecnologia (Ph.D. Grant SFRH/BD/69390/2010). This is also a contribution to MINECO Plan Nacional grant AGL2014-56305 and FEDER, and to the EU FP7 grant ANTIGONE # 278976

Hierarchal Characterization and Generation of Blogosphere Workloads

We present a thorough characterization of the access patterns in blogspace, which comprises a rich interconnected web of blog postings and comments by an increasingly prominent user community that collectively define what has become known as the blogosphere. Our characterization of over 35 million read, write, and management requests spanning a 28-day period is done at three different levels. The user view characterizes how individual users interact with blogosphere objects (blogs); the object view characterizes how individual blogs are accessed; the server view characterizes the aggregate access patterns of all users to all blogs. The more-interactive nature of the blogosphere leads to interesting traffic and communication patterns, which are different from those observed for traditional web content. We identify and characterize novel features of the blogosphere workload, and we show the similarities and differences between typical web server workloads and blogosphere server workloads. Finally, based on our main characterization results, we build a new synthetic blogosphere workload generator called GBLOT, which aims at mimicking closely a stream of requests originating from a population of blog users. Given the increasing share of blogspace traffic, realistic workload models and tools are important for capacity planning and traffic engineering purposes.UOL (Bolsa Pesquisa 20060520221328a); National Science Foundation (072064, 0735974, 0524477, 0520166, 0205294