Why logical clocks are easy

Tracking causality should not be ignored. It is important in the design of many distributed algorithms. And not respecting causality can lead to strange behaviors for users. The most commonly used mechanisms for tracking causality, vector clocks and version vectors, are simply optimized representations of causal histories, which are easy to understand. By building on the notion of causal histories, users can begin to see the logic ehind these mechanisms, to identify how they differ, and even consider possible optimizations. When confronted with an unfamiliar causality tracking mechanism, or when trying to design a new system that requires it, readers should ask two simple questions, which events need tracking and how does the mechanism translate back to a simple causal history.We would like to thank Rodrigo Rodrigues, Marc Shapiro, Russell Brown, Sean Cribbs, and Justin Sheehy for their feedback. This work was partially supported by EU FP7 SyncFree project (609551) and FCT/MCT projects UID/CEC/04516/2013 and UID/EEA/50014/2013.info:eu-repo/semantics/publishedVersio

Challenging the Computational Metaphor: Implications for How We Think

This paper explores the role of the traditional computational metaphor in our thinking as computer scientists, its influence on epistemological styles, and its implications for our understanding of cognition. It proposes to replace the conventional metaphor--a sequence of steps--with the notion of a community of interacting entities, and examines the ramifications of such a shift on these various ways in which we think

An experiment in software reliability

The results of a software reliability experiment conducted in a controlled laboratory setting are reported. The experiment was undertaken to gather data on software failures and is one in a series of experiments being pursued by the Fault Tolerant Systems Branch of NASA Langley Research Center to find a means of credibly performing reliability evaluations of flight control software. The experiment tests a small sample of implementations of radar tracking software having ultra-reliability requirements and uses n-version programming for error detection, and repetitive run modeling for failure and fault rate estimation. The experiment results agree with those of Nagel and Skrivan in that the program error rates suggest an approximate log-linear pattern and the individual faults occurred with significantly different error rates. Additional analysis of the experimental data raises new questions concerning the phenomenon of interacting faults. This phenomenon may provide one explanation for software reliability decay

Sustainability in HPC: Vision and Opportunities

Tackling climate change by reducing and eventually eliminating carbon emissions is a significant milestone on the path toward establishing an environmentally sustainable society. As we transition into the exascale era, marked by an increasing demand and scale of HPC resources, the HPC community must embrace the challenge of reducing carbon emissions from designing and operating modern HPC systems. In this position paper, we describe challenges and highlight different opportunities that can aid HPC sites in reducing the carbon footprint of modern HPC systems.Comment: Accepted at the ACM Sustainable Supercomputing Workshop in conjunction with SC'2

Challenges in Software Evolution

Today’s information technology society increasingly relies on software at all levels. Nevertheless, software quality generally continues to fall short of expectations, and software systems continue to suffer from symptoms of aging as they are adapted to changing requirements and environments. The only way to overcome or avoid the negative effects of software aging is by placing change and evolution in the center of the software development process. In this article we describe what we believe to be some of the most important research challenges in software evolution. The goal of this document is to provide novel research directions in the software evolution domain

Decision support for incorporating counter-terrorism design innovations into public places

Due to the prevailing threat of terrorism both internationally and within the UK, the British government has recently redeveloped the CONTEST strategy for countering international terrorism into a new and robust form known as CONTEST2. As part of this strategy, the UK government is encouraging those responsible for the protection of the public and ensuring the resilience of public buildings and crowded public areas to incorporate Counter-Terrorism (CT) measures where appropriate. However, it is apparent that there has been a lack of investment and ‘buy in’ from some key stakeholders. This is due largely to: client scepticism about the use of obtrusive, highly visible and unattractive solutions; a lack of informed guidance; differing opinions on the severity of the perceived threat from terrorism; and poor awareness of the cost-benefits of such measures. The outputs from a two year project, that has utilised a pluralistic methodology, are presented in the form of a web-based Decision Support Framework (DSF). The DSF has been developed by three English universities in collaboration with the British security services. The main purpose is to ensure that good practice in the design of effective and acceptable resilient public places can be more widely adopted. The DSF achieves this by providing individuals involved with the planning, design, construction, operation and management of public places with informed guidance on the necessity and use of CT measures; and supporting their operational activities towards the structured and proportionate integration of CT solutions into the varied design, build, operation and management processes. An evaluation of the DSF suggests that it promotes the innovation of passive and more acceptable CT measures, whilst simultaneously maintaining public safety. This greatly promotes the equal weighing of total expected benefits of CT measures against the total expected costs

Carbon and water footprint for the recycling process of expanded polystyrene (EPS) post-consumer waste

[Abstract] Plastic pollution of the natural environment is ubiquitous, and around 40% of all plastic waste produced globally is used in single-use products and only 9% is recycled. From this plastic waste, expandable polystyrene single-use products pose a major problem because of its great volume and low density. To abord this issue, the authors proposed a circular economy model for EPS post-consumer waste in 2019 through a case study with the help of one local plastic manufacturer. Although the idea of promoting circularity of this waste seems a priori to have a good impact on the environment, the process to reincorporate reused and/or recycled materials under the concept of CE have economic and environmental impacts on the environment that should be measured. To understand if a recycling process is truly beneficial to the environment, first we need to do a sustainability analysis, using sustainability indicators, such as Carbon Footprint (CF) and Water Footprint (WF). The objective of the present paper is to perform a sustainability analysis of the expandable polystyrene post-consumer recycling into resin pellets using CF and WF as sustainability indicators. We proposed three case scenarios considering an artisanal recycling with 2019 (A), and 2027 proposed electricity power mix (B), industrial recycling with current 2019 electricity power mix (C) and the use of virgin PS and its destination in landfill to compare. We measured the CO2 emissions and m3 of freshwater with the help of SimaPro 9.1 software. Overall, the total CO2 emissions for the case scenarios A and B are approximately 42% and 16% higher than scenario D, but scenario C exhibits a reduction of almost 50%. For the water depletion, scenarios A and B show very higher values than those of scenario D with 536% and 534%, respectively. Important to mention that scenario B presents much better values for CF than scenario A, meaning that the increase in the share of electricity production by renewable energies can improve the sustainable production of recycled PS resin

Whither Digital Archaeological Knowledge? The Challenge of Unstable Futures

Digital technology increasingly pervades all settings of archaeological practice and virtually every stage of knowledge production. Through the digital we create, develop, manage and share our disciplinary crown jewels. However, technology adoption and digital mediation has not been uniform across all settings or stages. This diversity might be celebrated as reflecting greater openness and multivocality in the discipline, but equally it can be argued that such diversity is unsustainable, and that standards are insufficiently rigorous. Regardless, all positions face the possibility of being severely tested by some large-scale external event: on every continent we witness economic and political upheaval, violence and social conflict. How is digitally mediated knowledge created, managed, and disseminated by archaeologists today, and how secure are the means by which this is achieved? To investigate this question we apply the futurity technique of scenario analysis to generate plausible scenarios and assess their strategic strengths and weaknesses. Based on this analysis we propose some measures to place archaeology in a more robust knowledgescape without stifling digitally creative disruption

Japan-ness + Suchness:: Seeking to Seize an Understanding of an Ethereal Elusive Ethos

Japan is in many ways a mysterious society with a rich history and complex culture. Informed by longstanding traditions and deeply-rooted values, contemporary Japan struggles to chart paths forward while retaining strong threads binding yesterday to tomorrow. Modern planning, architecture and design in Japan, and perhaps most notably in its capital city of Tokyo, in many ways illuminates the tensions that exist between the authority of the past and the promise of the future. Inspired in part by pervasive spiritual paths, fundamentally Shintoism and Buddhism, design embraces notions of ephemerality, impermanence and non-attachment. It also characterizes the pursuit and acceptance of perfection through imperfection. Wabi-Sabi and similar approaches highlight a high degree of comfort with the uncertain, the flawed and the incomplete. That said, remarkable advances in high-technology and an aggressive uptake of digital media counter this acceptance of the indeterminate, both in social and physical spheres. People are increasingly connected and informed, yet ironically disconnected and unaware. While society writ-large is shaped by intense formal and informal expectations to conform (the nail the stands out gets hammered down), it also permits ample latitude for the proliferation of subcultures and the acceptance of the extraordinary. Metabolist Architecture, for example, demonstrated an unbridled openness to utopian vision, bold departures and iconic gestures. The present research, through meta-analysis of the literature, case studies and logical argumentation, critically examines the notions of ‘Japan-ness' and ‘suchness' in light of current turbulence and transformations. The author, an architect and psychologist with extensive first-hand experience of Japan, considers a spectrum of dimensions that serve to distinguish and define the country and culture. Viewed through scholarly lenses that include architecture, education, spirituality and homelessness, the paper delineates and interprets the many qualities of Japan that continue to uphold its interwoven veils of mystery, sensuality, advancement and atmosphere. The paper seeks to demonstrate how architecture and urbanism in Japan embodies historic, spiritual and cultural values & practices. Using Tokyo as one window into such aspects, the author explores a variety of facets of the metropolis that illustrate those qualities that contribute to ‘Japan-ness'. Discussion includes implications/impacts to an annual study abroad program in architecture and planning whereby graduate students search for contextual understanding and cultural meaning prior to embarking on dramatic and diverse urban design projects. Designing, in a studio setting, in such a complicated and charged milieu demands a willingness to know and a commitment to connect. The deliverables of the research include the portrayal of a series of features of Japan-ness woven into an approach for understanding the conditions, complexities and characteristics of this leading nation and its incomparable culture. The systems- oriented multi-pronged tactic, and its underpinning information, proves valuable for researchers, educators, students and visitors examining, discovering and engaging Japan

The emerging of new business culture: A few key issues pertain to open economy and marketing

There is no question that the open source way of doing business has many distinct advantages over the traditional proprietary economy. Sharing IP (intellectual property) in an open economy is great but there has to be a return on the investment to create that IP. We examine the positive and negative aspects of the shift from industrial era capitalist proprietary business practices to a tribal form of an open source based "open economy", and explore some key issues pertain to open economy and marketing