Reliability and fault-tolerance by choreographic design

Distributed programs are hard to get right because they are required to be open, scalable, long-running, and tolerant to faults. In particular, the recent approaches to distributed software based on (micro-)services where different services are developed independently by disparate teams exacerbate the problem. In fact, services are meant to be composed together and run in open context where unpredictable behaviours can emerge. This makes it necessary to adopt suitable strategies for monitoring the execution and incorporate recovery and adaptation mechanisms so to make distributed programs more flexible and robust. The typical approach that is currently adopted is to embed such mechanisms in the program logic, which makes it hard to extract, compare and debug. We propose an approach that employs formal abstractions for specifying failure recovery and adaptation strategies. Although implementation agnostic, these abstractions would be amenable to algorithmic synthesis of code, monitoring and tests. We consider message-passing programs (a la Erlang, Go, or MPI) that are gaining momentum both in academia and industry. Our research agenda consists of (1) the definition of formal behavioural models encompassing failures, (2) the specification of the relevant properties of adaptation and recovery strategy, (3) the automatic generation of monitoring, recovery, and adaptation logic in target languages of interest.peer-reviewe

A Dynamic Fault Tolerance Model for Microservices Architecture

Microservices architecture is popular for its distributive system styles due to the independent character of each of the services in the architecture. Microservices are built to be single and each service has its running process and interconnecting with a lightweight mechanism that called application programming interface (API). The interaction through microservices needs to communicate internally. Microservices are a service that is likely to become unreachable to its consumers because, in any distributed setup, communication will fail on occasions due to the number of messages passing between services. Failures can occur when the networks are unreliable, and thus the connections can be latent which may lead to failure or slow response. This might be a problem for synchronous remote calls actively waiting for a response. If they do not use a proper timeout mechanism, they may end up waiting for an extended amount of time. Applications usually set a timeout for all remote calls to avoid hanging of the whole application due to network failure or component failure. However, this timeout needs to be set carefully to make the system or microservice application to work as required. This would prevent further problems because if a remote call is waiting too long for a reply, it can slow down the system in its entirety, and if a connection timeout is extremely fast, it may ignore a response that is sent after timeout. This thesis proposes a dynamic fault tolerance (DFTM) Model to improve the stability and resilience of the microservices architecture. The Model is designed using a two-states Circuit Breaker called Switch Circuit Breaker with Markov-Chain. In addition, a modified Circuit Breaker (three states – open, closed, and half-open) to Switch Circuit Breaker (two states – open and closed) is presented here. The Circuit Breaker uses timeout to detect fault but timeouts usage hinges on assumptions about the real-time behavior of the system and awaiting process can be deduced from the occurrence of a timeout that a failure has occurred. Therefore, DFTM model adopted Markov Chain based model to detect fault without a timeout. Then, it sends the fault directly to Switch Circuit Breaker that uses a 2-states to cover the faults. An important finding is that the DFTM model presents a solution to the problem of transient failures or faults in the interservice communication of microservices architecture. Also, it improves the performance and reliability of microservices architecture

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

The Effect of Group Work on Expressive-Artistic Activities for the Emotional Regulation of University Students

The purpose of higher education is the development of basic and professional skills to prepare students for the following stages of life. Social abilities and emotional regulation are considered to be part of these skills and could be improved through a group-work method. The aim of this study is to describe the emotional regulation process perceived by university students after group work is realised in expressive-artistic activities. The 69 participants (28 women and 41 men) aged between 19 and 26 (mean age 20.5, SD 2.1) were all second-year students of a Physical Activity and Sport Science degree. The data were collected through the questionnaire AIRE (Adaptative Instrument for Regulation of Emotions) applied by online form. The results revealed that the main goal of the students was to enjoy and have fun during the group work and gain new ideas from their peers. The biggest struggle was the schedule because some of them presented other personal or family commitments that limited their availability to practice. Overall, most of the participants affirmed that there are completely satisfied with the group project. In conclusion, group work within expressive-artistic activities improves social interaction and social skills but could be influenced by external factors (family, work, and other social commitments).This research was founded by the Program Redes-13CE for Research in University Teaching, from the Institute on Education Sciences of the University of Alicante (call 2020-21). Ref: [R37926]

Distribution pattern-driven development of service architectures

Distributed systems are being constructed by composing a number of discrete components. This practice is particularly prevalent within the Web service domain in the form of service process orchestration and choreography. Often, enterprise systems are built from many existing discrete applications such as legacy applications exposed using Web service interfaces. There are a number of architectural configurations or distribution patterns, which express how a composed system is to be deployed in a distributed environment. However, the amount of code required to realise these distribution patterns is considerable. In this paper, we propose a distribution pattern-driven approach to service composition and architecting. We develop, based on a catalog of patterns, a UML-compliant framework, which takes existing Web service interfaces as its input and generates executable Web service compositions based on a distribution pattern chosen by the software architect

Faculty Publications and Creative Works 1997

One of the ways we recognize our faculty at the University of New Mexico is through this annual publication which highlights our faculty\u27s scholarly and creative activities and achievements and serves as a compendium of UNM faculty efforts during the 1997 calendar year. Faculty Publications and Creative Works strives to illustrate the depth and breadth of research activities performed throughout our University\u27s laboratories, studios and classrooms. We believe that the communication of individual research is a significant method of sharing concepts and thoughts and ultimately inspiring the birth of new of ideas. In support of this, UNM faculty during 1997 produced over 2,770 works, including 2,398 scholarly papers and articles, 72 books, 63 book chapters, 82 reviews, 151 creative works and 4 patents. We are proud of the accomplishments of our faculty which are in part reflected in this book, which illustrates the diversity of intellectual pursuits in support of research and education at the University of New Mexico. Nasir Ahmed Interim Associate Provost for Research and Dean of Graduate Studie

Reversible Computation: Extending Horizons of Computing

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first

Chapter 59: Web Services

Web services are a cornerstone of the distributed computing infrastructure that the VO is built upon yet to the newcomer, they can appear to be a black art. This perception is not helped by the miasma of technobabble that pervades the subject and the seemingly impenetrable high priesthood of actual users. In truth, however, there is nothing conceptually difficult about web services (unsurprisingly any complexities will lie in the implementation details) nor indeed anything particularly new. A web service is a piece of software available over a network with a formal description of how it is called and what it returns that a computer can understand. Note that entities such as web servers, ftp servers and database servers do not generally qualify as they lack the standardized description of their inputs and outputs. There are prior technologies, such as RMI, CORBA, and DCOM, that have employed a similar approach but the success of web services lies predominantly in its use of standardized XML to provide a language-neutral way for representing data. In fact, the standardization goes further as web services are traditionally (or as traditionally as five years will allow) tied to a specific set of technologies (WSDL and SOAP conveyed using HTTP with an XML serialization). Alternative implementations are becoming increasingly common and we will cover some of these here. One important thing to remember in all of this, though, is that web services are meant for use by computers and not humans (unlike web pages) and this is why so much of it seems incomprehensible gobbledegook. In this chapter, we will start with an overview of the web services current in the VO and present a short guide on how to use and deploy a web service. We will then review the different approaches to web services, particularly REST and SOAP, and alternatives to XML as a data format. We will consider how web services can be formally described and discuss how advanced features such as security, state and asynchrony can be provided. Note that much of this material is not yet used in the VO but features heavily in IVOA discussions on advanced services and capabilities

The Development of a Musculoskeletal Profiling Tool to Guide Entry into Classical Ballet

The classical ballet profession requires both athleticism and artistry in a professional dancer with a physique that satisfies the aesthetic demands of the artform. Intensive training starts very young in vocational schools, but injury rates and attrition are high. Based on the consensus of a modified Delphi Survey sent out internationally to enquire about the most frequently selected attributes in the professional dancer, a battery of musculoskeletal assessment tests, some already in use, was selected. A focus group of experts was consulted to advise on suitability for inclusion in the audition profile prior to entry into vocational training. Fourteen range of movement (ROM) and functional movement control (FMC) tests were trialled on eighteen preprofessional ballet students (16 – 17 years) who had newly entered training. Three experienced physiotherapists conducted a repeated assessment, and reliability studies were carried out. Intra- and inter-rater reliability was calculated. The intraclass correlation coefficient (Model 3,1), standard error of measurement and minimal detectable change were used to calculate the intra-rater reliability. The continuous measures were also divided into categories and the alpha coefficient was used. The filmed FMC tests were scored, and the Kappa coefficient was calculated. Intra-rater reliability was moderate to excellent for ROM (ICC = .614 - .970) and substantial to excellent for the FMC (Cohen’s kappa = .670 – 1.000). The inter-rater reliability for hip rotation reached moderate acceptability only on the right (ICC = .515 - .622) and spinal extension in the second round (ICC = .584). When continuous measurements were categorised and the Alpha Coefficient was used, hip rotation was acceptable on both sides and both rounds (.616 - .856). For spinal extension the Alpha Coefficient was acceptable at .748. The inter-rater reliability of the three FMC tests was acceptable (.449 - .820) but the ballet technique-based tests resulted in low agreement with Raters 1 and 3 only, reaching moderate agreement (.410 - .654). The modified plank test was fair to moderate (.347 - .471) in spite of excellent intra-rater reliability (.838 – 1.000). The use of categories when measuring ROM is recommended to improve agreement between raters. Scoring functional movement requires practise by therapists to improve reliability, and familiarity with technical movements in ballet requires physiotherapists to develop specialist skills. Standardised, reliable tests are recommended to capture each physique and its particular combination of attributes, including spine, hip and plantarflexion. Decision making at audition can be supported and facilitated