Experimenting with Gnutella Communities

Computer networks and distributed systems in general may be regarded as communities where the individual components, be they entire systems, application software or users, interact in a shared environment. Such communities dynamically evolve with components or nodes joning and leaving the system. Their own individual activities affect the community's behaviour and vice-versa. This paper discusses various experiments undertaken to investigate the behaviour of a real system, the Gnutella network, which represents such a community. Gnutella is a distributed Peer-to-Peer data-sharing system without any central control. It turns out that most interactions between nodes do not last long and much of their activity is devoted to finding appropriate partners in the network. Good connections lasting longer appear only as rare events. For example, out of 42,000 connections only 57 hosts were found to available on a regular basis. This means that, in contrast to the common belief that this kind of peer-to-peer networks or sub-communities are always large, they are actually quite small. However, those sub-communities examplify very dynamic behaviour because their actual composition can change very quickly. The experimental results presented have been obtained from a Java implementation of Gnutella running in the open Internet environment, and thus in unknown and quickly changing network structures heavily dependent on chance. Les réseaux informatique ainsi que les systèmes distribués peuvent être considérés comme des communautés où les composantes - que ce soit des systèmes complets, des programmes ou des usagers - interagissent dans un environnement partagé. Ces communautés sont dynamiques car des éléments peuvent s'y joindre ou quitter en tout temps. L'article présente les résultats d'une suite d'expériences et de mesures faites sur Gnutella, un système peer-to-peer à grande échelle qui opère sans aucun contrôle centralisé. Nous avons remarqué qu'une grande partie des messages échangés sont erronés ou redondants et que les interactions entre n?uds ne durent pas très longtemps. En particulier, des connexions durant plus d'une minute sont des phénomènes rares. Les n?uds passent donc la majorité de leur temps à remplacer les partenaires perdus et, contrairement à l'idée répandue que les réseaux peer-to-peer sont immenses, nous avons noté que les communautés effectives étaient assez limitées. Gnutella est un environnement très dynamique avec peu de stabilité. Par exemple, de 42,000 sites avec lesquels nous avons établi une connexion, il a seulement été possible de re-communiquer de façon régulière avec 57. Dans un tel environnement, la chance joue un rôle important dans la performance observée; mais nous avons élaboré un protocole expérimental permettant de comparer diverses options.Gnutella, peer-to-peer networks, Internet communities, distributed systems, protocols, Gnutella, réseaux peer-to-peer, communautés virtuelles, internet, systèmes distribués, protocoles de télécommunication

Process-based indicators to assess storm induced coastal hazards

Storms are responsible for several hazards (e.g. overwash, erosion, inundation) in coastal areas, leading to the destruction of property and loss of life in populated areas. Various indicators are used to express potential storm impact and describe the associated hazards. The most commonly used indicators include either forcing parameters (e.g. wave height, sea level) or coastal morphologies (e.g. dune height or berm width). Whereas they do not represent the processes associated with storm induced hazards in coastal areas. Alternatively, a hazard could be better characterised if process-based indicators are used instead. Process-based indicators express the result of the forcing mechanisms acting over the coastal morphology and reflect both hydrodynamic and morphological characteristics. This work discusses and synthesizes the most relevant process-based indicators for sandy shores subject to overwash, erosion and inundation promoted by storms. Those include: overwash depth, potential and extent; shoreline, berm or dune retreat; vertical erosion; and inundation depth and extent. The selection of a reduced set of process-based indicators to identify coastal hazards induced by storms in sandy coasts will facilitate comparison of different coastal behaviours for distinct storm return periods, and help to optimise coastal management plans, thereby contributing to the reduction of coastal risks.info:eu-repo/semantics/publishedVersio

Characterizing user behavior in online social networks: Analysis of the regular use of Facebook

The analysis of user behaviour in online social networks (OSNs) is one of the important research interests related to human-computer interactions. OSNs gives a large space to share news with no limits around the world and allows user to benefit from properties of this interactive and dynamic system. The study of user behaviour on a social and popular platform characterized by the use of new technologies requires to understand and the analysis of collective behaviour on Facebook. This paper aims to analyse the usage patterns in OSNs using the visible interactions of Facebook, by studying the time of activity and the evolution of human behaviour through a process of detection of visible and non-volatile interactions. In the first step, we perform a data collection process based on breadth first search algorithm (BFS) and semi-supervised crawler agent. In the second step, we build an interaction quantification process to measure users’ activities and analysis related time series. The study of the frequency of periodic use has shown that the communities monitored follow a weekly rhythm that decreases over time to reach a frequency of daily use, which reflects a stability of activities and a case of dependency of use

Mass Collaboration and Learning: Structure and Methods

The rapid emergence of social networks and collaborative communities supported by the Internet and associated innovative technologies, and the increasing demand for continuous improvement and fostering lifelong learning have led to unprecedented waves of novelty in the ways people create and share knowledge in different spheres. In this regard, mass collaboration (MC) through Internet-based solutions has opened new windows of opportunity to collaborate massively and learn collectively in ways that seemed impossible even a few decades ago. Learning ecosystems can benefit from mass collaboration where large numbers of minds collectively drive intellectual efforts to learn in the form of knowledge building and sharing. Mass collaborative learning (MCL) is a new paradigm that represents a significant shift away from the traditional teacher-centered approach towards a self-directed model in virtual communities in which contributing members take on creative roles to maximize their learning and that of their peers. Furthermore, MCL provides greater opportunities for distributed contributors to engage in virtual global learning and take the advantage of powerful social communities of experts and counterparts. Even though MCL opens up an apparently limitless field for promoting social inclusion in effective learning, not all aspects, features, and characteristics of this phenomenon are quite clear and discovered at present. In order to design, implement, and exploit such a learning approach, influencing constituents should be identified, and appropriate conditions need to be provided. However, existing literature offers limited information, guidance, and support for the creation, operation, coordination, and development of MCL initiatives. In this context, there are a number of identified critical issues, specific problems, gaps, and inconsistencies, and this thesis is correspondingly conducted to propose a Meta-Governance framework for MCL initiatives (MGF-MCL). This framework, by benefiting from various other related ideas, models, and methods, tries to give further insights into an integrated perspective of the most complex concerning issues and also some internal and external aspects of governance for the MCL initiatives. Furthermore, the MGF-MCL intends to provide some directions, guidance, and support for the implementation, operation, and development of MCL initiatives. In this thesis work, in order to (a) guide our research endeavor, (b) concretize our research design, (c) design, develop, validate, and apply the MGF-MCL, and (d) understand the practical value of our findings, we have followed the design science research process (DSRP) approach. We have evaluated the validity and applicability of the MGF-MCL through a mix of methods namely, case studies in EU projects, peer-review publications, and an MCL illustration case. A number of scenarios made within the case studies have brought together several industry and academic experts to evaluate the validity and applicability of MGF-MCL. The peer reviews of contributed publications also assessed the quality of the work and helped to establish the validity of MGF-MCL based upon the expert knowledge of other researchers. The MCL illustration case provided empirical evidence, relying on observation and experimentation. In terms of research, the findings of our work offer direction and support for the creation, operation, and implementation of MLC initiatives.A rápida emergência de redes sociais e comunidades colaborativas apoiadas pela Internet e tecnologias inovadoras associadas, e a crescente procura de melhorias contínuas e a promoção da aprendizagem ao longo da vida levaram a ondas de inovação sem precedentes na forma como as pessoas criam e partilham conhecimentos em diferentes esferas. A este respeito, a colaboração em massa (MC) através de soluções baseadas na Internet abriu novas janelas de oportunidade para colaborar massivamente e aprender colectivamente de formas que pareciam impossíveis mesmo há algumas décadas atrás. Os ecossistemas de aprendizagem podem beneficiar da colaboração em massa, onde grandes números de mentes impulsionam colectivamente os esforços intelectuais para aprender sob a forma de construção e partilha de conhecimento. A aprendizagem colaborativa em massa (MCL) é um novo paradigma que representa uma mudança significativa da abordagem tradicional centrada no professor para um modelo auto-dirigido em comunidades virtuais em que os membros contribuintes assumem papéis criativos para maximizar a sua aprendizagem e a dos seus pares. Além disso, a MCL oferece maiores oportunidades a contribuintes geograficamente distribuídos para se envolverem na aprendizagem global virtual e tirarem partido das ricas comunidades sociais de especialistas e homólogos. Embora a MCL abra um campo aparentemente ilimitado para promover a inclusão social na aprendizagem efectiva, nem todos os aspetos, facetas e características deste fenómeno são totalmente claros e conhecidos actualmente. A fim de conceber, implementar, e explorar uma tal abordagem de aprendizagem, devem ser identificados os constituintes relevantes, e devem ser criadas condições de suporte apropriadas. Contudo, a literatura existente apenas oferece de forma limitada informação, orientação e apoio para a criação, operação, coordenação e desenvolvimento de iniciativas MCL. Neste contexto, há uma série de questões críticas, problemas específicos, lacunas e inconsistências identificados, e esta tese é correspondentemente desenvolvida para propor um quadro de Meta-Governança para iniciativas MCL (MGF-MCL). Este quadro, ao beneficiar de várias outras ideias, modelos e métodos relacionados, tenta fornecer uma perspectiva integrada das questões mais complexas e também de alguns aspectos internos e externos de governação para as iniciativas MCL. Além disso, o MGF-MCL pretende fornecer alguma orientação e apoio para a implementação, operação e desenvolvimento das iniciativas MCL. Neste trabalho de tese, a fim de (a) orientar o nosso esforço de investigação, (b) concretizar o nosso projecto de investigação, (c) conceber, desenvolver, validar, e aplicar o MGF-MCL, e (d) compreender o valor prático dos resultados, seguimos a abordagem do "DESIGN SCIENCE RESEARCH PROCESS" (DSRP). Avaliámos a adequação e aplicabilidade do MGF-MCL através de uma combinação de métodos, nomeadamente, estudos de caso em projetos da UE, publicações com revisão por pares e, um caso de ilustração MCL. Vários cenários feitos no âmbito dos estudos de caso envolveram vários peritos da indústria e da academia para avaliar a validade e a aplicabilidade do MGF-MCL. As revisões por pares das publicações produzidas neste trabalho também permitiram aferir a qualidade do trabalho e ajudaram a estabelecer a validade do MGF-MCL com base no conhecimento especializado de outros investigadores. O caso da ilustração de MCL forneceu uma evidência empírica, apoiando-se na observação e experimentação. Em termos de investigação, os resultados do nosso trabalho oferecem orientação e apoio para a criação, operação e implementação de iniciativas MLC

A Model for Comparative Analysis of Business Community Expectations of Printing Companies and Printer Perceptions of Those Expectations

The problem of this study was to compare the Statesboro, Georgia business community\u27s expectations of printing companies to the expectations printers perceive the businesses have. All of the local printers, and a sample of the local Chamber of Commerce corporate members (non-printers) were given identical survey forms which measured their expectations and perceptions. The forms were hand-delivered, picked-up the next day and tabulated to put the data in graphical form. A comparison of the two groups revealed some agreement and some disagreement in expectations and perceptions. After completing the study, it was determined that the research method is valid and produces information that can be used by the printing industry. Implementation of similar studies in other industries should be a valid method for analysis of business expectations as compared with how those expectations are perceived by the industry

EPIC-DB: a proteomics database for studying Apicomplexan organisms

<p>Abstract</p> <p>Background</p> <p>High throughput proteomics experiments are useful for analyzing the protein expression of an organism, identifying the correct gene structure of a genome, or locating possible post-translational modifications within proteins. High throughput methods necessitate publicly accessible and easily queried databases for efficiently and logically storing, displaying, and analyzing the large volume of data.</p> <p>Description</p> <p>EPICDB is a publicly accessible, queryable, relational database that organizes and displays experimental, high throughput proteomics data for <it>Toxoplasma gondii </it>and <it>Cryptosporidium parvum</it>. Along with detailed information on mass spectrometry experiments, the database also provides antibody experimental results and analysis of functional annotations, comparative genomics, and aligned expressed sequence tag (EST) and genomic open reading frame (ORF) sequences. The database contains all available alternative gene datasets for each organism, which comprises a complete theoretical proteome for the respective organism, and all data is referenced to these sequences. The database is structured around clusters of protein sequences, which allows for the evaluation of redundancy, protein prediction discrepancies, and possible splice variants. The database can be expanded to include genomes of other organisms for which proteome-wide experimental data are available.</p> <p>Conclusion</p> <p>EPICDB is a comprehensive database of genome-wide <it>T. gondii </it>and <it>C. parvum </it>proteomics data and incorporates many features that allow for the analysis of the entire proteomes and/or annotation of specific protein sequences. EPICDB is complementary to other -genomics- databases of these organisms by offering complete mass spectrometry analysis on a comprehensive set of all available protein sequences.</p

Growing the future of agriculture: an examination of knowledge-sharing and community building in the fresh produce and floral council

This study examines knowledge-sharing practices within a community of practice (CoP) through a case study of the Fresh Produce and Floral Council (FPFC). The study sought to investigate how the FPFC promoted agricultural knowledge and expertise, impacted its members\u27 social relationships and knowledge-sharing practices, communicated clear roles and expectations, and provided valuable and accessible resources. A mixed-methods approach was employed to investigate the research questions, which involved conducting a survey and utilizing descriptive statistics, frequencies, and Spearman correlations to analyze both the Likert scale and open-ended responses. The findings suggested that the FPFC has a knowledge-sharing culture promoting active participation and collaboration among members, with room for improvement in knowledge-sharing practices. Additionally, FPFC positively impacts members\u27 social relationships and prioritizes knowledge-sharing, with a need for further education and promotion of these benefits. Also, clear communication of roles and expectations is essential in any CoP. There may be a need to further clarify the community\u27s goals and purpose to ensure member engagement and alignment. Finally, members perceived FPFC\u27s resources as valuable and relevant, but there is a need for improvement in their accessibility and availability. Overall, the study provided valuable insights for developing new methods of knowledge-sharing and onboarding within the agriculture industry to address the aging crisis and ensure the industry\u27s future. Thus, it was essential to explore the value of knowledge-sharing practices and technology for communication within the community to contribute to developing virtual CoPs enabling knowledge transfer and relationship building for agriculture professionals

On Estimating the Effects of Increased Aid to Education

[Excerpt] The 1983 report, A Nation at Risk, of the National Commission on Excellence in Education decried the state of public education in the United States and suggested a number of reforms. Among their recommendations was increased federal aid for education. The view was that this would lead to desirable outcomes such as reduced class sizes and higher teacher salaries, with the latter aiding in the recruitment and retention of high-quality teachers. Somewhat surprisingly, previous research on the economics of education provides us with very few insights about what the effects of such proposals might be. For example, while there is an extensive literature on the determinants of cross-section variations in teachers\u27 salaries and teacher/student ratios, virtually nothing has been written on how changes in aid levels influence changes in salaries, teacher/student ratios, other expenditure levels, and local tax rates. Similarly, while there are many studies of how grants-in-aid affect overall expenditure levels and some studies of the determinants of cross-section variations in the share of expenditures spent on various categories (e.g., instructional and administrative), virtually nothing has been written on how changes in aid affect the various expenditure shares. To provide answers to some of these questions, our paper examines data from a panel of approximately 700 school districts in New York State over a five-year period (1978-79 to 1982-83) and tries to infer how school districts will respond to future changes in aid from how they responded to changes in state aid during the period. We focus on how past aid changes have influenced teacher salaries, tax rates, teacher/student ratios, and other staff/student ratios. The analyses exploit the fact that although school aid formulas change frequently in New York State, each district is usually guaranteed at least the same aid level as the previous year ( save harmless provisions). As a result, over any given two-year period, the percentage increase in aid varies widely across districts. This provides a convenient form of natural experiment