The aDORe federation architecture: digital repositories at scale

The need to federate repositories emerges in two distinctive scenarios. In one scenario, scalability-related problems in the operation of a repository reach a point beyond which continued service requires parallelization and hence federation of the repository infrastructure. In the other scenario, multiple distributed repositories manage collections of interest to certain communities or applications, and federation is an approach to present a unified perspective across these repositories. The high-level, 3-Tier aDORe federation architecture can be used as a guideline to federate repositories in both cases. This paper describes the architecture, consisting of core interfaces for federated repositories in Tier-1, two shared infrastructure components in Tier-2, and a single-point of access to the federation in Tier-3. The paper also illustrates two large-scale deployments of the aDORe federation architecture: the aDORe Archive repository (over 100,000,000 digital objects) at the Los Alamos National Laboratory and the Ghent University Image Repository federation (multiple terabytes of image files).     

实时在线交互应用的体系结构与状态一致性

实时在线交互应用（ROIA）是近年国外学者提出的一类新的分布式应用,包括交互式E learning系统和大型多人在线游戏（MMOG）在内的多种应用系统都是ROIA的典型应用。国外对ROIA及其典型应用MMOG研究较多,而国内虽然MMOG产业发展势头强劲但在该领域的相关研究却相对较少,因此对ROIA及其关键技术进行研究有一定的理论意义和现实意义。先对ROIA体系结构的研究现状进行了系统的分类总结,并比较分析了各体系结构优缺点。之后,讨论了ROIA实现中的关键问题--状态一致性问题。深入分析了ROIA中两种基本的一致性模型,并介绍了ROIA主流部署模式C/MS下的一致性维护的研究现状。     

Predictive accuracy comparison of fuzzy models for software development effort of small programs

Regression analysis to generate predictive equations for software development effort estimation has recently been complemented by analyses using less common methods such as fuzzy logic models. On the other hand, unless engineers have the capabilities provided by personal training, they cannot properly support their teams or consistently and reliably produce quality products. In this paper, an investigation aimed to compare personal Fuzzy Logic Models (FLM) with a Linear Regression Model (LRM) is presented. The evaluation criteria were based mainly upon the magnitude of error relative to the estimate (MER) as well as to the mean of MER (MMER). One hundred five small programs were developed by thirty programmers. From these programs, three FLM were generated to estimate the effort in the development of twenty programs by seven programmers. Both the verification and validation of the models were made. Results show a slightly better predictive accuracy amongst FLM and LRM for estimating the development effort at personal level when small programs are developed.     

Evolution styles: foundations and models for software architecture evolution

As new market opportunities, technologies, platforms, and frameworks become available, systems require large-scale and systematic architectural restructuring to accommodate them. Today’s architects have few techniques to help them plan this architecture evolution. In particular, they have little assistance in planning alternative evolution paths, trading off various aspects of the different paths, or knowing best practices for particular domains. In this paper, we describe an approach for planning and reasoning about architecture evolution. Our approach focuses on providing architects with the means to model prospective evolution paths and supporting analysis to select among these candidate paths. To demonstrate the usefulness of our approach, we show how it can be applied to an actual architecture evolution. In addition, we present some theoretical results about our evolution path constraint specification language.     

Sustaining complementor engagement in digital platform ecosystems: Antecedents,behaviours and engagement trajectories

Digital platform ecosystems increasingly dominate the enterprise software domain, and the persistence of platforms depends on the sustained engagement of complementors. However, there is a limited understanding of its antecedents, complementors' evaluation of antecedents and the manifestations and dynamic changes of complementors' engagement. Therefore, we investigate complementors' engagement within platform ecosystems over time. We draw on actor and stakeholder engagement from service research to conceptualise complementor engagement (CE) and create an integrated empirical understanding of CE and its dynamics in digital platform ecosystems. Our embedded case study builds on 30 interviews with complementors in Anubis and Osiris enterprise software platform ecosystems. Inductive data analysis reveals five CE antecedents: platform resources and rules, platform value proposition, platform agents, customer needs and other complementors' value propositions. The antecedents are associated with three CE behaviours: generating, networking and synchronising. Further analysis of CE over time resulted in 26 different sequences representing stable and changing engagement trajectories, the latter comprising selective, growing and abating engagement as subcategories. We show how complementors' evaluations of antecedents lead to behaviour changes, providing a novel perspective on the dynamics underlying CE. Finally, we link complementors' evaluation outcomes to their (dis)satisfaction, contributing to the discussion on what drives and impedes CE. The findings implicate the debate on dynamic platform governance and inform platform owners about using cooperative and competitive approaches in the short and long term.     

Sequential architecture models for Prolog: A performance comparison

In this paper we investigate the relation between architectural support for Prolog and performance. We will show that partial support for tags does perform as well as full support, but it only reduces the execution time by approximately 10%. With respect to special addressing modes, auto address modification (post/pre increment, decrement on loads and stores) only yields a cycle reduction of approximately 6% and the introduction of a single shadow register set yields around 8%. Combining these optimizations, a performance gain of 20 to 25% can be achieved, depending on the memory system. Usingvliw techniques, which exploit instruction-level parallelism, the performance can be doubled, using three processing elements. Two processing elements already provide a significant speedup, but the use of four processing elements is not justified if we compare the gain in performance with the cost of the extra hardware. In general we observe only a small performance improvement (around 20%) when moving fromrisc to special-purposerisc architectures, an improvement which can also be achieved by applying advanced compiler technology, such as compiler optimization, optimizations forwam, and optimal scheduling techniques forvliw architectures. Unfortunately these hardware and software effects do not add up, as a better compiler reduces the effect of hardware support. Finally, the cycle time is essential for comparing the performance of different (micro)-architectures, but it is not always clear what the effects of the different tradeoffs are on the maximum achievable cycle time.     

Understanding the role of licenses and evolution in open architecture software ecosystems

The role of software ecosystems in the development and evolution of open architecture systems whose components are subject to different licenses has received insufficient consideration. Such systems are composed of components potentially under two or more licenses, open source or proprietary or both, in an architecture in which evolution can occur by evolving existing components, replacing them, or refactoring. The software licenses of the components both facilitate and constrain the system's ecosystem and its evolution, and the licenses’ rights and obligations are crucial in producing an acceptable system. Consequently, software component licenses and the architectural composition of a system help to better define the software ecosystem niche in which a given system lies. Understanding and describing software ecosystem niches for open architecture systems is a key contribution of this work. An example open architecture software system that articulates different niches is employed to this end. We examine how the architecture and software component licenses of a composed system at design time, build time, and run time help determine the system's software ecosystem niche and provide insight and guidance for identifying and selecting potential evolutionary paths of system, architecture, and niches.     

Big data and business analytics ecosystems: paving the way towards digital transformation and sustainable societies

The digitalization process and its outcomes in the 21st century accelerate transformation and the creation of sustainable societies. Our decisions, actions and even existence in the digital world generate data, which offer tremendous opportunities for revising current business methods and practices, thus there is a critical need for novel theories embracing big data analytics ecosystems. Building upon the rapidly developing research on digital technologies and the strengths that information systems discipline brings in the area, we conceptualize big data and business analytics ecosystems and propose a model that portraits how big data and business analytics ecosystems can pave the way towards digital transformation and sustainable societies, that is the Digital Transformation and Sustainability (DTS) model. This editorial discusses that in order to reach digital transformation and the creation of sustainable societies, first, none of the actors in the society can be seen in isolation, instead we need to improve our understanding of their interactions and interrelations that lead to knowledge, innovation, and value creation. Second, we gain deeper insight on which capabilities need to be developed to harness the potential of big data analytics. Our suggestions in this paper, coupled with the five research contributions included in the special issue, seek to offer a broader foundation for paving the way towards digital transformation and sustainable societies     

From enterprise architecture to business models and back

In this study, we argue that important IT change processes affecting an organization’s enterprise architecture are also mirrored by a change in the organization’s business model. An analysis of the business model may establish whether the architecture change has value for the business. Therefore, in order to facilitate such analyses, we propose an approach to relate enterprise models specified in ArchiMate to business models, modeled using Osterwalder’s Business Model Canvas. Our approach is accompanied by a method that supports business model-driven migration from a baseline architecture to a target architecture and is demonstrated by means of a case study.     

Mobile business models: organizational and financial design issues that matter

Designing viable mobile services and business models that capture value for all the organizations involved is a challenge. There are many design issues that can be taken into account, and it is often unclear what their ultimate effect is on the performance of a business model. This paper offers a framework for relating critical design issues to success factors and tests the causal relationship between these core concepts in the organizational and financial domain of mobile business models, based on an international survey among 120 practitioners and experts in the mobile Internet services domain, most of them from EU countries. According to our findings, addressing organizational design issues (i.e. partner selection, governance and relation management) leads to an acceptable division of roles among actors, while addressing financial design issues (i.e., pricing, division of investments and costs among partners) results in risk levels that are perceived to be acceptable. The level of profitability that is perceived to be acceptable is influenced indirectly by these design issues, because the relationships are mediated through the risk level that the actors involved perceive to be acceptable and through the way the roles are divided among the actors.      

Numerical study of stress-transport turbulence models: Implementation and validation issues

The primary goal of this work is to implement, validate and compare in shear-free and simple wall-bounded turbulent flows the performance of five stress-transport turbulence models that have recently appeared in the open literature. A secondary goal of this work is to analyze and study the effort and difficulties encountered by programmers when implementing turbulence models developed by other researchers. The need for standardized procedures and for the development of efficient numerical techniques is advocated as a means to reduce the model-variance and code dependency of turbulent models. The second-order models chosen for this study are the Launder-Shima, the Jakirlic-Hanjalic, the elliptic-blending model of Manceau, the Turbulent Potential Model proposed by Perot and an unidentified model. For comparison reasons, Wilcox k-ω eddy-viscosity model was included in the study. The validation and the study of the performance of the models were performed through the comparison of the numerical solutions with experimental data and analytical solutions. The five benchmark flowfields considered in this study encompass the shear-free and wall-bounded regimes and are the flat plate without pressure gradient, the flow over a plate with a moderately adverse pressure gradient, and the self-similar flows of the mixing layer, the plane jet and the axi-symmetric jet. The tested stress-transport models produced results in general agreement with the experiments. However, no clear advantage of the stress-transport model over Wilcox k-ω model was noticed in these simple flowfields. The Launder-Shima model could not predict accurately the skin friction on a flat plate but it performed well in all the other cases. Although the test cases used were simple, a major difficulty encountered in this effort is the unreliability of the open literature as a resource for turbulence model implementation. A general lack of consistency was observed between model versions published in different journals or at different times. The detrimental effect that such a lack of structure and consistency has on the CFD community is discussed.     

High integrity software development: process and tool issues

YSE and BAe Defence have recently completed an unclassified study for MoD (PE) specifically concerned with high integrity software development process and tool issues. The overall objective of the project was to produce guidance for MoD project managers on the sorts of processes and toolsets which their suppliers should be expected to deploy on projects being conducted in the context of Interim Defense Standard (IDS) 00-55 and IDS 00-56. A wide-ranging survey of industrial practice underpinned the project.This paper reports the main areas of work of the project and its results. The topics covered include:

• •⊗ ideal high integrity software development including tool support requirements;
• •⊗ a review of current high integrity software development practice;
• •⊗ available tool support (COTS and proprietary);
• •⊗ a minimum acceptable process and associated tool support;
• •⊗ process and toolset hazard analysis;
• •⊗ process and toolset safety cases;
• •⊗ building better toolsets;
• •⊗ process and toolset assessment.

     

A framework for discovering and classifying ubiquitous services in digital health ecosystems

A digital ecosystem is a widespread type of ubiquitous computing environment comprised of ubiquitous, geographically dispersed, and heterogeneous species, technologies and services. As a subdomain of the digital ecosystems, digital health ecosystems are crucial for the stability and sustainable development of the digital ecosystems. However, since the service information in the digital health ecosystems exhibits the same features as those in the digital ecosystems, it is difficult for a service consumer to precisely and quickly retrieve a service provider for a given health service request. Consequently, it is a matter of urgency that a technology is developed to discover and classify the health service information obtained from the digital health ecosystems. A survey of state-of-the-art semantic service discovery technologies reveals that no significant research effort has been made in this area. Hence, in this paper, we present a framework for discovering and classifying the vast amount of service information present in the digital health ecosystems. The framework incorporates the technology of semantic focused crawler and social classification. A series of experiments are conducted in order to respectively evaluate the framework and the employed mathematical model.