Webbing and orchestration. Two interrelated views on digital tools in mathematics education

The integration of digital tools in mathematics education is considered both promising and problematic. To deal with this issue, notions of webbing and instrumental orchestration are developed. However, the two seemed to be disconnected, and having different cultural and theoretical roots. In this article, we investigate the distinct and joint journeys of these two theoretical perspectives. Taking some key moments in recent history as points of de- parture, we conclude that the two perspectives share an importance attributed to digital tools, and that initial differences, such as different views on the role of digital tools and the role of the teacher, have become more nuances. The two approaches share future chal- lenges to the organization of teachers'collaborative work and their use of digital resources.Comment: Teaching Mathematics and its Applications (2014) to be complete

Quality-aware model-driven service engineering

Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Quality aspects ranging from interoperability to maintainability to performance are of central importance for the integration of heterogeneous, distributed service-based systems. Architecture models can substantially influence quality attributes of the implemented software systems. Besides the benefits of explicit architectures on maintainability and reuse, architectural constraints such as styles, reference architectures and architectural patterns can influence observable software properties such as performance. Empirical performance evaluation is a process of measuring and evaluating the performance of implemented software. We present an approach for addressing the quality of services and service-based systems at the model-level in the context of model-driven service engineering. The focus on architecture-level models is a consequence of the black-box character of services

An architecture for certification-aware service discovery

Service-orientation is an emerging paradigm for building complex systems based on loosely coupled components, deployed and consumed over the network. Despite the original intent of the paradigm, its current instantiations are limited to a single trust domain (e.g., a single organization). Also, some of the key promises of service-orientation - such as the dynamic orchestration of externally provided software services, using runtime service discovery and deployment - are still unachieved. One of the main reasons for this is the trust gap that normally arises when software services, offered by previously unknown providers, are to be selected at run-time, without any human intervention. To close this gap, the concept of machine-readable security certificates (called asserts) has been recently introduced, which paves the way to automated processing about security properties of services. Similarly to current security certification schemes, the assessment of the security properties of a service is delegated to an independent third party (certification authority), who issues a corresponding assert, bound to the service. In this paper, we propose an architecture, which exploits the assert concept to realise a certification-aware service discovery framework. The architecture supports the discovery of single services based on certified security properties (in additional to the usual functional properties), as well as the dynamic synthesis of service compositions, that satisfy the given security properties. The architecture is extensible, thus allowing for a range of domain specific matchmaking components, to cover dimensions related to, e.g., performance, cost and other non-functional characteristics

Multi-level Service Approach for Flexible Support of Design Processes

Part III: Sustainable ServicesInternational audienceThe need to answer quickly to new market opportunities and the high variability of consumer demands tend industrial companies to review their adopted organisation, so to improve their reactivity and to facilitate the coupling with the business enactment. Therefore, these companies require agility in their information systems to allow business needs scalability and design process flexibility. We propose in this paper, the business activities as a service based on the service paradigm and whereas a design process is made of agile services orchestrations. We discuss the interest to use a service-oriented approach and propose a layered architecture for design process enactment

The computational complexity of QoS measures for orchestrations

The final publication is available at link.springer.comWe consider Web services defined by orchestrations in the Orc language and two natural quality of services measures, the number of outputs and a discrete version of the first response time. We analyse first those subfamilies of finite orchestrations in which the measures are well defined and consider their evaluation in both reliable and probabilistic unreliable environments. On those subfamilies in which the QoS measures are well defined, we consider a set of natural related problems and analyse its computational complexity. In general our results show a clear picture of the difficulty of computing the proposed QoS measures with respect to the expressiveness of the subfamilies of Orc. Only in few cases the problems are solvable in polynomial time pointing out the computational difficulty of evaluating QoS measures even in simplified models.Peer ReviewedPostprint (author's final draft

Using formal methods to develop WS-BPEL applications

In recent years, WS-BPEL has become a de facto standard language for orchestration of Web Services. However, there are still some well-known difficulties that make programming in WS-BPEL a tricky task. In this paper, we firstly point out major loose points of the WS-BPEL specification by means of many examples, some of which are also exploited to test and compare the behaviour of three of the most known freely available WS-BPEL engines. We show that, as a matter of fact, these engines implement different semantics, which undermines portability of WS-BPEL programs over different platforms. Then we introduce Blite, a prototypical orchestration language equipped with a formal operational semantics, which is closely inspired by, but simpler than, WS-BPEL. Indeed, Blite is designed around some of WS-BPEL distinctive features like partner links, process termination, message correlation, long-running business transactions and compensation handlers. Finally, we present BliteC, a software tool supporting a rapid and easy development of WS-BPEL applications via translation of service orchestrations written in Blite into executable WS-BPEL programs. We illustrate our approach by means of a running example borrowed from the official specification of WS-BPEL

Distributed orchestration of user interfaces

Workflow management systems focus on the coordination of people and work items, service composition approaches on the coordination of service invocations, and, recently, web mashups have started focusing on the integration and coordination of pieces of user interfaces (UIs), e.g., a Google map, inside simple web pages. While these three approaches have evolved in a rather isolated fashion although they can be seen as evolution of the componentization and coordination idea from people to services to UIs in this paper we describe a component-based development paradigm that conciliates the core strengths of these three approaches inside a single model and language. We call this new paradigm distributed UI orchestration, so as to reflect the mashup-like and process-based nature of our target applications. In order to aid developers in implementing UI orchestrations, we equip the described model and language with suitable design, deployment, and runtime instruments, covering the whole life cycle of distributed UI orchestrations. © 2011 Elsevier Ltd. All rights reserved

DSOL: a declarative approach to self-adaptive service orchestrations

Service oriented computing (SOC) has brought a simplification in the way distributed applications can be built. Mainstream approaches, however, failed to support dynamic, self-managed compositions that would empower even non-technical users to build their own orchestrations. Indeed, because of the changeable world in which they are embedded, service compositions must be able to adapt to changes that may happen at run-time. Unfortunately, mainstream SOC languages, like BPEL and BPMN, make it quite hard to develop such kind of self-adapting orchestrations. We claim that this is mostly due to the imperative programming paradigm they are based on. To overcome this limitation we propose a radically different, strongly declarative approach to model service orchestration, which is easier to use and results in more flexible and self-adapting orchestrations. An ad-hoc engine, leveraging well-known planning techniques, interprets such models to support dynamic service orchestration at run-time

The Man Creates Instruments that Transform Himself: An Overview of GERE Research within Mathematics Education

This paper discusses GERE (Study Group on Resources for Education) members’ research trajectory in three different lines: Teaching practice and practice management, Teacher education and identity, and Support for learning and resource generation. It discusses how researchers seek to understand technology integration in the practice of distance education in Brazil, with the instrumental orchestrations lens, revealing the changes made in the didactic configurations, from the multiplicity of teachers responsible for each discipline. Teachers’ documentation is discussed in the process of resource elaboration and use and guided by design, experimentation, and reflection of the generated instrument, such as digital textbooks and mathematical games. The notion of integrating artefacts is discussed both from the perspective of collaborative learning and of instrumental meta-orchestration, a teacher education model about instrumental orchestration. Finally, thinking about the artefact as a support for learning also made us work on generating devices aimed at specific concepts such as covariation in learning functions