Feature-based Modelling of a Complex, Online-Reconfigurable Decision Support Service

In this paper, we show how the concepts of components, features and services are used today in the Online Conference System (OCS) in order to marry the modelling of functionally complex, online reconfigurable internet services at the application level with the needs of a model-driven development amenable to analyze and verify the models. Characteristic of the approach is the coarse-grained approach to modelling and design of features and services, which guarantees the scalability to capture large complex systems. The interplay of the different features and components is realized via a coordination-based approach, which is an easily understandable modelling paradigm of system-wide business processes, and thus adequate for the needs of industrial application developers.     

Metro Maps on Octilinear Grid Graphs

Schematic transit maps (often called “metro maps” in the literature) are important to produce comprehensible visualizations of complex public transit networks. In this work, we investigate the problem of automatically drawing such maps on an octilinear grid with an arbitrary (but optimal) number of edge bends. Our approach can naturally deal with obstacles that should be respected in the final drawing (points of interest, rivers, coastlines) and can prefer grid edges near the real-world course of a line. This allows our drawings to be combined with existing maps, for example as overlays in map services. We formulate an integer linear program which can be used to solve the problem exactly. We also provide a fast approximation algorithm which greedily calculates shortest paths between node candidates on the underlying octilinear grid graph. Previous work used local search techniques to update node positions until a local optimum was found, but without guaranteeing octilinearity. We can thus calculate nearly optimal metro maps in a fraction of a second even for complex networks, enabling the interactive use of our method in map editors.     

Involving users early on in the design process: closing the gap between mobile information services and their users

Designing mobile information services, including mobile Internet services, mobile banking, interactive mobile television, location-based services etc. that capture a mass market has not been easy, and there have been many disappointments over the past years. There are still uncertainties with regard to the kinds of mobile services users want and need. We argue that users wants and needs depend on their context, which means that users should play an important role in the design process of mobile information services, through a structured approach in which developers and users work together. In this paper, we present a group-based approach to include the user early on in the design process in an efficient way. We have applied the group-based approach in three cases, i.e. mobile services for campus visitors, wireless applications for the process industry and services for crisis management. In all cases, involving users early on in the design process enabled the developers to gather useful information for designing mobile information services.     

A Principled Approach to Grammars for Controlled Natural Languages and Predictive Editors

Controlled natural languages (CNL) with a direct mapping to formal logic have been proposed to improve the usability of knowledge representation systems, query interfaces, and formal specifications. Predictive editors are a popular approach to solve the problem that CNLs are easy to read but hard to write. Such predictive editors need to be able to “look ahead” in order to show all possible continuations of a given unfinished sentence. Such lookahead features, however, are difficult to implement in a satisfying way with existing grammar frameworks, especially if the CNL supports complex nonlocal structures such as anaphoric references. Here, methods and algorithms are presented for a new grammar notation called Codeco, which is specifically designed for controlled natural languages and predictive editors. A parsing approach for Codeco based on an extended chart parsing algorithm is presented. A large subset of Attempto Controlled English has been represented in Codeco. Evaluation of this grammar and the parser implementation shows that the approach is practical, adequate and efficient.     

Building Large,Complex, Distributed Safety-Critical Operating Systems

Safety-critical systems typically operate in unpredictable environments. Requirements for safety and reliability are in conflict with those for real-time responsiveness. Due to unpredictable environmental needs there is no static trade-off between measures to accommodate the conflicting objectives. Instead every feature or operating system service has to be adaptive. Finally, for any design problem, there cannot be any closed-form (formal) approach taking care at the same time of (external) time constraints or deadlines, and synchronization requirements in distributed design. The reason is that these two aspects are causally independent. - In this situation we worked out a heuristic experimental, performance-driven and performance-based methodology that allows in an educated way to start with a coarse system model, with accurate logical expectations regarding its behavior. Through experiments these expectations are validated. If they are found to successfully stand the tests extended expectations and model features are generated for refining the previous design as well as its performance criteria. The refinement is done in such a way that the previous experimental configurations are extreme model cases or data profiles which both logically and experimentally are to reproduce the behavior of the previous modeling step. Thus the novel performance aspects or tendencies could then unambiguously be attributed to the influences of the refined model features. We termed this methodology Incremental Experimentation. As a general methodology it relies on a principle of comparative performance studies rather than on realistic data for narrow application ranges. The paper describes how we applied a 5-step design and refinement procedure for developing, analyzing, and evaluating our distributed operating system MELODY that exhibits novel services for supporting real-time and safety-critical applications in unpredictable environments. Experimental set-ups and theme-related findings are discussed in particular.     

Design of a digital exchange

As part of the development of their proposed integrated services network, Network 2000, ITT have produced the 1240 digital exchange for voice and data. Hardware has been designed for a range of exchange sizes. LSI and commercially-available microprocessors are used. A distributed control structure provides the size range, and a modular approach allows the attachment of new or customized modules.Software has been designed to cover the full traffic range and telecommunications needs that will include voice, data, rural, local transit and toll applications. The system is intended to allow the simple implementation of design changes for technology and for the offering of new services.     

Appropriating virtual learning environments: A study of teacher tactics

In research on Virtual Learning Environments (VLEs), it has been shown that teachers often do not explore VLEs to their full potential and only adopt a limited set of the available tools. In this article, we approach teachers’ design of VLE learning activities as end user development. We describe a study of Toledo, a virtual learning environment used across several higher education institutions in Belgium. Using a combination of a semiotic, multimodal analysis and an in-depth user study with 24 respondents, we provide a detailed account of how teachers appropriate the learning environment to suit their needs. Combining the insights from the semiotic investigation and the user research, we analyze how user appropriations can be explained as practices emerging from both how the platform communicates, and contextual factors. The study showed that some teachers design very specific learning activities using the VLE - not by using the dedicated VLE tool, but by reinterpreting more generic tools. These appropriation tactics concentrate platform use in a limited number of tools, even when teachers do use more complex learning activities. These results have implications for the design of VLEs: rather than offering a wide range of tools targeted at specific learning activities, VLEs could concentrate on providing basic communication tools that are open for appropriation.     

User-centred design: for users or by users?

Abstract

When ergonomists contribute to the design of products and services they aim to be user-centred. This paper explores two possible meanings of user-centredness; the ergonomist may use theories and findings about human behaviour to act for the user or may help the user to participate in design. Both approaches are well known in ergonomics and they can point in conflicting directions. This paper examines the rationale for the two approaches and presents the results of a survey, which found that the most successful strategy was to mix the two approaches. It offers a classification to support the identification of the appropriate approach to adopt in different situations. The paper proposes, for example, that ‘design by users’ is the appropriate strategy when significant value judgements have to be taken in a local or bespoke design setting. By contrast a ‘design for users’ approach is appropriate for the design of generic products. An additional approach ‘design for users with users’ is introduced for settings that require knowledge about human characteristics and that need users to make value judgements.     

Adaptive tetrahedral remeshing for modified solid models

During the engineering design process, a designed engineering component is usually repeatedly modified and analyzed to reach final design objectives, and completely mesh regeneration for each design change is very time consuming. An efficient remeshing approach for modified solid models using existing prior existing meshes is proposed in this paper to resolve this issue. It is mainly achieved via three main steps: different face (between the input model and its modification) identification, local destruction zone generation, and local mesh regeneration. In this approach, by carefully selecting a destruction zone to be removed from the original mesh model, a final geometric adaptive mesh model of the modified model is generated, which is very important for downstream analysis accuracy control. Additionally, the complex boundary of the variation region that needs to be remeshed is set up by merging the boundaries of modified region and the destruction zone without using complex intersection operations, which ensure the approach’s robustness. Experimental results on practical engineering parts are also shown to demonstrate the method’s performance.     

Review of numerical computation of compressible flows with artificial interfaces

In Computational Fluid Dynamics, it is very often to use a composite grid for various purposes including easy meshing of a complex geometry, parallel computing, local mesh refinement, or treating different flows with different physical models, and using different numerical methods. All these methods have a common feature: they have internal artificial interfaces at which one needs to define interface conditions. In this paper, we first give a review on the current status of this subject with emphasis on compressible flows. Then two problems will be discussed in details. The first is for the overlapping grid approach due to its wide popularity for treating complex geometry and for parallel computing. The second is concerned with continuum/DSMC matching since this is a hot topic of current interest. A two dimensional computation is also performed to study the transmission of a shock wave across an overlapping grid interface.     

Intelligent dynamic workflow support for a ubiquitous Web service-based manufacturing environment

The ubiquitous environment is increasingly being considered as a platform for finding and integrating separate distributed services. Individuals or businesses can provide their services in the form of Web services in such a ubiquitous environment, and business processes that integrate such ubiquitous Web services can be formed using workflow technology. Workflow design and execution in such a dynamic and distributed environment needs to be very flexible in terms of incorporating changes. Web services may suddenly become unavailable and backup services may need to be found, or several providers of services may not be identifiable at the design time of the workflow. Therefore, dynamically finding and invoking Web services based on the workflow semantics need to be supported. BPEL4WS is the most popular and promising language among the workflow design languages for Web services. However, one of the problems with BPEL4WS is that it references the fixed WSDL file, which makes the workflow less flexible in dynamic and ubiquitous environments. Another problem is that it limits the amount of resources to only those that are specified. This makes it difficult to support semantics for finding similar or backup services in a ubiquitous network. This paper focuses on extending the BPEL4WS framework to include semantics by adding semantic constructs into WSDL and making use of ontologies in the BPEL4WS engine in order to support dynamic workflows suitable for ubiquitous environments.     

A design rationale for a language-based editor

This paper reviews the design issues that arise in the construction of effective language-based editors for the preparation of syntactically and static semantically correct language sentences, typically computer programs. The need for such editors to support a pluralistic view of program structure is identified, together with the need to observe the constraints on performance and storage consumption if such editors are to be accepted by professional programmers. From these basic needs, more specific requirements for the display, parsing and semantic checking components of such an editor are derived.     

A model-driven approach for facilitating user-friendly design of complex event patterns

Complex Event Processing (CEP) is an emerging technology which allows us to efficiently process and correlate huge amounts of data in order to discover relevant or critical situations of interest (complex events) for a specific domain. This technology requires domain experts to define complex event patterns, where the conditions to be detected are specified by means of event processing languages. However, these experts face the handicap of defining such patterns with editors which are not user-friendly enough. To solve this problem, a model-driven approach for facilitating user-friendly design of complex event patterns is proposed and developed in this paper. Besides, the proposal has been applied to different domains and several event processing languages have been compared. As a result, we can affirm that the presented approach is independent both of the domain where CEP technology has to be applied to and of the concrete event processing language required for defining event patterns.     

Log-based mining techniques applied to Web service composition reengineering

Web service compositions are becoming more and more complex, involving numerous interacting ad-hoc services. These services are often implemented as business processes themselves. By analysing such complex web service compositions one is able to better understand, control and eventually re-design them. Our contribution to this problem is a mining algorithm, based on a statistical technique to discover composite web service patterns from execution logs. Our approach is characterised by a “local” pattern’s discovery that covers partial results through a dynamic programming algorithm. Those locally discovered patterns are then composed iteratively until the composite Web service is discovered. The analysis of the disparities between the discovered model and the initial ad-hoc composite model (delta-analysis) enables initial design gaps to be detected and thus to re-engineer the initial Web service composition.     

Digital circles of support: Meeting the information needs of older people

The UK Government strategy for aging in the 21st Century challenges conceptions of older people as passive recipients of care and promotes their engagement as active citizens. The strategy includes a commitment to test services which embody these principles with a range of innovative pilot projects. This paper summarises research on older people’s information needs and use which informed the design for one of these projects, Leeds Link-Age Plus. The research explored the complex circumstances around which older people access and use social and community information – a topic that has received limited attention in the literature. The paper is novel in considering how the use of informal networks for securing information, advice and advocacy can be supported by technology literate mediators, who may be older people, located within local community or voluntary organisations. Emphasising the mediator in design facilitates social contacts, directly addresses issues of trust and can reduce the chance of causing distress dealing with complex information. A model is suggested for using emerging technology to introduce new ways in which information for older adults can be improved by digital ‘circles of support’ – a form of social network where mediators collaborate to create and share self-authored content.     

Flexible decision support in dynamic inter-organisational networks

An effective Decision Support System (DSS) should help its users improve decision making in complex, information-rich environments. We present a feature gap analysis that shows that current decision support technologies lack important qualities for a new generation of agile business models that require easy, temporary integration across organisational boundaries. We enumerate these qualities as DSS Desiderata, properties that can contribute both effectiveness and flexibility to users in such environments. To address this gap, we describe a new design approach that enables users to compose decision behaviours from separate, configurable components, and allows dynamic construction of analysis and modelling tools from small, single-purpose evaluator services. The result is what we call an ‘evaluator service network’ that can easily be configured to test hypotheses and analyse the impact of various choices for elements of decision processes. We have implemented and tested this design in an interactive version of the MinneTAC trading agent, an agent designed for the Trading Agent Competition for Supply Chain Management.     

一种动态无线传感网络操作系统－SOS

无线传感器网络节点,在一般用途的系统和嵌入式系统里都有自己的特点。有时必须在能源很少并且环境比较恶劣的情况下工作,同时还提供共同服务,使它很容易编写应用程序。在当前流行的无线传感网络操作系统TinyOs下,虽然各个组件可以互相提供共同服务,但是每个传感器节点必须单独的运行一个静态的系统镜像,所以很难满足多维应用的系统或者频繁的应用更新。SOS,一种从设计上更考虑动态性的更适合微型节点的操作系统应运而生。它由一个公共的内核和模块组成,它有自己的消息机制．动态内存机制,可以动态加载和动态卸载模块,以及其他的一些服务。然而模块之间是通过一个相互的预定协作机制相互联系的．没有内存的保护。但是尽管如此,SOS通过一系列自己的手段有效的克服了这些缺点,比如看门狗定时器,垃圾回收系统等等。相互独立的模块之间,可以通过最小的系统终端来添加或者删除。通过对比,虽然SOS是动态设计并且使用了更高的内核接口．但是跟TinyOs相比,总的使用开销却是基本一样的。SOS是基于模块化的,容易编程。TinyOS是基于组件化,效率高。而MantisOS可以支持多线程,但是代码占用空间大。由此可以看到,SOS是一个具有自己的特点和优势的无线传感网络操作系统。     

The future of systems research

After 20 years in academia and the Silicon Valley, the new Provost of Stanford University calls for a shift in focus for systems research. Performance-long the centerpiece-needs to share the spotlight with availability, maintainability, and other qualities. Although performance increases over the past 15 years have been truly amazing, it will be hard to continue these trends by sticking to the basically evolutionary path that the research community is currently on. The author advocates a more evolutionary approach to systems problems and thinks the approach needs to be more integrated. Researchers need to think about hardware and software as a continuum, not as separate parts. He sees society on the threshold of a “post PC” era, in which computing is ubiquitous, and everyone will use information services and everyday utilities. When everyone starts using these systems, guess what? They expect them to work and to be easy to use. So this era will drive system design toward greater availability, maintainability, and scalability, which will require a real refocusing of current research directions