Blockchain and Cryptocurrencies: a Classification and Comparison of Architecture Drivers

Blockchain is a decentralized transaction and data management solution, the technological leap behind the success of Bitcoin and other cryptocurrencies. As the variety of existing blockchains and distributed ledgers continues to increase, adopters should focus on selecting the solution that best fits their needs and the requirements of their decentralized applications, rather than developing yet another blockchain from scratch. In this paper we present a conceptual framework to aid software architects, developers, and decision makers to adopt the right blockchain technology. The framework exposes the interrelation between technological decisions and architectural features, capturing the knowledge from existing academic literature, industrial products, technical forums/blogs, and experts' feedback. We empirically show the applicability of our framework by dissecting the platforms behind Bitcoin and other top 10 cryptocurrencies, aided by a focus group with researchers and industry practitioners. Then, we leverage the framework together with key notions of the Architectural Tradeoff Analysis Method (ATAM) to analyze four real-world blockchain case studies from industry and academia. Results shown that applying our framework leads to a deeper understanding of the architectural tradeoffs, allowing to assess technologies more objectively and select the one that best fit developers needs, ultimately cutting costs, reducing time-to-market and accelerating return on investment.Comment: Accepted for publication at journal Concurrency and Computation: Practice and Experience. Special Issue on distributed large scale applications and environment

Trust and exchange : the production of trust in illicit online drug markets

Au cours de la dernière décennie, les marchés illicites en ligne sont passés de niches de marchés à plateformes économiques à part entière. L’un des aspects de cette expansion semble reposer dans l’abandon de l’articulation traditionnelle de la relation de confiance entre vendeurs et acheteurs pour l’adoption de transactions régies par les principes d’atomisation sociale et d’anonymat. Se situant au cœur d’une sociologie économique des marchés illicites encore émergente, cette thèse cherche donc à étudier l’élaboration de la confiance au sein des marchés de drogues illicites en ligne. En m’appuyant sur la notion d’institutions en tant que constructions sociales, j'avance la thèse selon laquelle ces marchés illicites modernisent les modalités de transaction des marchés licites traditionnels : des contrats sont proposés ; des tribunaux sont érigés; la sanction est formalisée ; et la gouvernance est transformée. Cette approche permet de révéler un schisme fondamental de la littérature et de ses postulats à l’égard de l'ordre social régnant au sein des marchés illicites en ligne -- rupture qui s’exprime notamment par l’opposition entre 1) une conception de ces marchés comme socialement atomisés et régis uniquement par la réputation ; et 2) l’idée selon laquelle les serveurs restent sous le contrôle des administrateurs. Afin de pallier cette discordance, je propose un modèle d’élaboration de la confiance notamment issu des approches cognitives et comportementales. Premièrement, je soutiens qu'un ensemble de mécanismes actifs de renforcement remplace fonctionnellement les principes sociaux traditionnels de la confiance. Deuxièmement, je soutiens que la confiance, aussi bien interpersonnelle qu’abstraite (à savoir, la confiance accordée aux institutions), est principalement produite selon un processus bayésien d'accumulation d'expériences. Dans cette perspective, l'article « Uncertainty and Risk » examine l'ensemble des mécanismes actifs de renforcement de la confiance -- première composante de ce modèle -- et révèle que les vendeurs ajustent les prix non seulement en fonction de la réputation, mais également des contrats et du statut. Dans les articles suivants, le processus bayésien d'accumulation d'expériences -- deuxième partie du modèle -- est abordé. L’étude menée dans l‘article « Building a case for trust » met ainsi en lumière une association entre les échanges répétés avec le vendeur et une tendance à effectuer des transactions de plus en plus importantes. Le troisième article (« A change of expectations? »), quant à lui, met en exergue le fait qu’un faible nombre d’expériences satisfaisantes suffit à augmenter la certitude de l’acheteur quant à la qualité du produit illicite. Dans leur ensemble, ces deux articles soutiennent l’idée selon laquelle le processus d'accumulation d'expériences favorise la coopération et les attentes. Enfin, ce travail s’achève par l’articulation des deux composantes de ce modèle et, de manière plus générale, par l’articulation de la thèse de la modernisation et d’une conception de la confiance dont l’élaboration repose sur un processus d’accumulation d’expériences sociales. L’apport unique d'une sociologie économique dans l’étude criminologique des marchés illicites est notamment souligné et des pistes de recherches futures sont discutées.During the last decade illicit online drug markets have grown from niche markets into full-fledged platform economies. It seems that over the course of a few years, sellers and buyers have left the social bases of trust behind preferring to exchange under conditions of social atomization and anonymity. Situated in an emerging economic sociological approach to illicit markets, this work examines the production of trust in illicit online drug markets. Drawing on economic sociology, namely, the notion of institutions as social constructions, I advance the thesis that these markets modernize the premodern exchange modes of traditional illicit markets: Contracts are implemented; courts are erected; sanctions are formalized; and governance transforms. This analysis reveals a fundamental schism in the literature and its assumptions about the social order of illicit online markets. Specifically, a conception of these markets as socially atomized and governed only by reputation, versus the recognition that servers remain under the control of administrators. Building off the modernization thesis and the schism, I propose a model for the production of trust that is sensitive to both cognitive and behavioral approaches to trust. First, I propose that a set of active trust producing mechanisms functionally replace the bases of trust that have eroded as illicit markets move online. Second, I argue that trust is primarily produced through a Bayesian process of accumulating experience, which produces both interpersonal and abstract trust. In the article Uncertainty and Risk I examine the first component, the active production of trust. I revisit a key debate in the literature, the pricing of illicit goods. We find that sellers set prices adjust prices not only with respect to reputation, but also contracts and status. In the following two articles, I examine the second part of the model, the bayesian process of experience accumulation. In the article Building a Case for Trust, I find that repeated exchanges with a seller are associated with a propensity towards larger transactions. In the third article, A Change of Expectations?, I find that even a few experiences increases expectations in the performance of the market institution. Thus, the two articles provide evidence that the process of experience accumulation promotes cooperation and expectation. I conclude the work by reconciling a tension between the two components of the model, the proposition that markets are modernized, but that trust is produced primarily through a process of experience accumulation. On this basis, I continue to highlight the contributions and analytical advantages of the economic sociological approach to illicit markets

JURI SAYS:An Automatic Judgement Prediction System for the European Court of Human Rights

In this paper we present the web platform JURI SAYS that automatically predicts decisions of the European Court of Human Rights based on communicated cases, which are published by the court early in the proceedings and are often available many years before the final decision is made. Our system therefore predicts future judgements of the court. The platform is available at jurisays.com and shows the predictions compared to the actual decisions of the court. It is automatically updated every month by including the prediction for the new cases. Additionally, the system highlights the sentences and paragraphs that are most important for the prediction (i.e. violation vs. no violation of human rights)

Semantic discovery and reuse of business process patterns

Patterns currently play an important role in modern information systems (IS) development and their use has mainly been restricted to the design and implementation phases of the development lifecycle. Given the increasing significance of business modelling in IS development, patterns have the potential of providing a viable solution for promoting reusability of recurrent generalized models in the very early stages of development. As a statement of research-in-progress this paper focuses on business process patterns and proposes an initial methodological framework for the discovery and reuse of business process patterns within the IS development lifecycle. The framework borrows ideas from the domain engineering literature and proposes the use of semantics to drive both the discovery of patterns as well as their reuse