普适计算环境下服务组合及部署的研究

普适计算（Pervasive Computing）的出现改变了传统的以计算机为中心的资源和信息获取模式，提出一种以人为本的计算方式，为人们提供随时随地、适应环境变化的资源和信息的获取方法，成为下一代网络的主流发展方向之一。普适计算具有环境异构并且动态变化的特点，在这种网络环境中信息的开发和集成打破了传统的模式，软件变服务的观点被普遍接受，并且得到了广泛的应用。因此，面向服务的计算（Service-oriented Computing）和普适计算的结合，是未来信息技术的下一阶段，也成为目前研究的热点问题。 一方面针对普适计算的特点，研究其动态变化、移动性和用户相关性等；一方面针对面向服务的计算，研究其体系结构、服务的描述、查询、组合、部署等问题。普适计算的特点决定了在该环境下的服务组合需要适应环境的动态变化；服务部署需要满足资源约束条件，提高网络资源利用率。基于研究背景以及对目前存在问题的分析，本文进行普适计算环境下服务组合及部署的研究，主要工作包括以下四个方面： （1）提出了一种规则驱动上下文相关的服务组合方法 服务组合是面向服务的计算中经典问题，研究成果包括组合模型、语言、方法和系统等，根据需求提出基于工作流、基于形式化方法、基于语义以及基于服务非功能属性等多种服务组合方法，但这些方法难以解决普适计算中的服务组合问题。因为在普适计算环境下，服务组合不仅需要满足功能性要求，而且要适应环境的异构和动态变化，能够根据环境变化自动的构建组合路径并动态的绑定服务。本文使用上下文刻画普适计算的动态变化性，提出一种基于本体的上下文模型和描述语言，并扩展服务描述，将上下文引入服务组合，提出服务组合算法，实现了规则驱动上下文相关的服务组合路径的建立。 （2）提出一种基于上下文协商的动态服务选取方法 服务组合路径建立了服务执行的先后顺序，在服务的执行期间需要动态的绑定实例，绑定服务实例过程称为动态的服务选取。考虑到普适计算中设备资源有限性以及提高网络资源利用率，本文提出一种基于上下文协商的服务选取方法。首先从已有的上下文本体中获取与动态服务选取相关的上下文，并根据其内容的不同分为用户上下文、设备上下文和服务上下文；然后给出上下文协商的约束条件，基于约束条件提出了上下文的协商算法，进行服务的选取绑定，实现动态服务组合。最后通过实验验证了算法的效率和有效性，分析了上下文数目和服务数目的变化，对服务组合成功率、资源利用率、服务选择冲突率等的影响。 （3）提出普适计算环境下的服务动态部署问题及算法 某些特定的应用（如数字家庭等）需要将服务部署在一个普适计算环境中，部署时需要考虑网络中负载均衡，提高资源利用率。本文针对普适计算中设备异构、资源有限的特点，给出组合服务动态部署问题的描述，并说明该问题是一个NP问题，提出一个启发式算法，能够在多项式时间内找到近似最优解，最后通过算法模拟和实验验证了算法的有效性以及时间性能，说明该方法适用于设备或者原子服务数目较多的普适计算环境。 （4）实现了一个服务组合原型系统 本文在国家八六三项目和国家科技攻关项目研究的基础上，实现了一个服务组合原型系统，该系统是“Web服务计算平台”的一部分，并以分布式文档管理系统为例，给出了服务组合的实现效果。

Electronic Business Contracts between Services

Electronic contracts mirror the paper versions exchanged between businesses today, and offer the possibility of dynamic, automatic creation and enforcement of restrictions and compulsions on service behaviour that are designed to ensure business objectives are met. Where there are many contracts within a particular application, it can be difficult to determine whether the system can reliably fulfil them all, yet computer-parsable electronic contracts may allow such verification to be automated. In this chapter, we describe a conceptual framework and architecture specification in which normative business contracts can be electronically represented, verified, established, renewed, and so on. In particular, we aim to allow systems containing multiple contracts to be checked for conflicts and violations of business objectives. We illustrate the framework and architecture with an aerospace aftermarket example.

Defending grid web services from XDoS attacks by SOTA

Grid Web Services are still relevantly a new to business systems, and as more systems are being attached to it, any threat to it could bring collapse and huge harm. Some of these potential threats to Grid Web services come in a new form of a new denial of service attack (DoS), called XML Denial of Service or XDOS attacks. Though, as yet, there have not been any reported attacks from the media, we have observed these attacks are actually far less complex to implement than any previous Denial of Service (DoS), but still just as affective. Current security applications for grid web services (WS-Security for example), based on our observations, and are not up to job of handling the problem. In this paper, we build on our previous work called Service Oriented Traceback Architecture (SOTA), and apply our model to Grid Networks that employ web services. We further introduce a filter defence system, called XDetector, to work in combination with SOTA. Our results show that SOTA in conjunction with XDetector makes for an effective defence against XDoS attacks and upcoming DXDoS.

Experiences gained from building a services-based distributed operating system

The goal of this paper is to present the experiences gained over 15 years of research into the design and development of a services-based distributed operating system. The lessons learnt over this period, we hope, will be of value to researchers involved in the design and development of operating systems that wish to harness the collective resources of ever-expanding distributed systems.

Cloud Integrator: uma plataforma para composição de serviços em ambientes de computação em nuvem

With the advance of the Cloud Computing paradigm, a single service offered by a cloud platform may not be enough to meet all the application requirements. To fulfill such requirements, it may be necessary, instead of a single service, a composition of services that aggregates services provided by different cloud platforms. In order to generate aggregated value for the user, this composition of services provided by several Cloud Computing platforms requires a solution in terms of platforms integration, which encompasses the manipulation of a wide number of noninteroperable APIs and protocols from different platform vendors. In this scenario, this work presents Cloud Integrator, a middleware platform for composing services provided by different Cloud Computing platforms. Besides providing an environment that facilitates the development and execution of applications that use such services, Cloud Integrator works as a mediator by providing mechanisms for building applications through composition and selection of semantic Web services that take into account metadata about the services, such as QoS (Quality of Service), prices, etc. Moreover, the proposed middleware platform provides an adaptation mechanism that can be triggered in case of failure or quality degradation of one or more services used by the running application in order to ensure its quality and availability. In this work, through a case study that consists of an application that use services provided by different cloud platforms, Cloud Integrator is evaluated in terms of the efficiency of the performed service composition, selection and adaptation processes, as well as the potential of using this middleware in heterogeneous computational clouds scenarios

Geração de processos WS-BPEL com base em um algoritmo de reescrita de regras

Web services are computational solutions designed according to the principles of Service Oriented Computing. Web services can be built upon pre-existing services available on the Internet by using composition languages. We propose a method to generate WS-BPEL processes from abstract specifications provided with high-level control-flow information. The proposed method allows the composition designer to concentrate on high-level specifi- cations, in order to increase productivity and generate specifications that are independent of specific web services. We consider service orchestrations, that is compositions where a central process coordinates all the operations of the application. The process of generating compositions is based on a rule rewriting algorithm, which has been extended to support basic control-flow information.We created a prototype of the extended refinement method and performed experiments over simple case studies

A language for self-adaptive system requirements

Self-adaptive systems have the capability to autonomously modify their behaviour at run-time in response to changes in their environment. Such systems are now commonly built in domains as diverse as enterprise computing, automotive control systems, and environmental monitoring systems. To date, however, there has been limited attention paid to how to engineer requirements for such systems. As a result, selfadaptivity is often constructed in an ad-hoc manner. In this paper, we argue that a more rigorous treatment of requirements relating to self-adaptivity is needed and that, in particular, requirements languages for self-adaptive systems should include explicit constructs for specifying and dealing with the uncertainty inherent in self-adaptive systems. We present some initial thoughts on a new requirements language for selfadaptive systems and illustrate it using examples from the services domain. © 2008 IEEE.

Enhancing cloud computing environments using a cluster as a service

The emergence of cloud computing has caused a significant change in how IT infrastructures are provided to research and business organizations. Instead of paying for expensive hardware and incur excessive maintenance costs, it is now possible to rent the IT infrastructure of other organizations for a minimal fee. While the existence of cloud computing is new. The elements used to create clouds have been around for some time. Cloud computing systems have been made possible through the use of large-scale clusters, service-oriented architecture (SOA), Web services, and virtualization. While the idea of offering resources via Web services is commonplace in cloud computing, little attention has been paid to the clients themselves specifically, human operators. Despite that clouds host a variety of resources which in turn are accessible to a variety of clients, support for human users is minimal.

Business and software service lifecycle management

Although the service-oriented paradigm has been well established in the technical domain for quite some time now, service governance is still considered a research gap. To ensure adequate governance, there is a necessity to manage services as first-class assets throughout the lifecycle. Now that the concept of ser-vice-orientation is also increasingly applied on the business level to structure an organisation’s capabili-ties, the problem has become an even bigger chal-lenge. This paper presents a generic business and software service lifecycle and aligns it with the com-mon management layers in organisations. Using ser-vice analysis as an example, it moreover illustrates how activities in the service lifecycle may vary on lower levels of granularity depending on the focus on business or software services.

Towards a unified service description language for the internet of services : requirements and first developments

Service-oriented Architectures (SOA) and Web services leverage the technical value of solutions in the areas of distributed systems and cross-enterprise integration. The emergence of Internet marketplaces for business services is driving the need to describe services, not only from a technical level, but also from a business and operational perspective. While, SOA and Web services reside in an IT layer, organizations owing Internet marketplaces are requiring advertising and trading business services which reside in a business layer. As a result, the gap between business and IT needs to be closed. This paper presents USDL (Unified Service Description Language), a specification language to describe services from a business, operational and technical perspective. USDL plays a major role in the Internet of Services to describe tradable services which are advertised in electronic marketplaces. The language has been tested using two service marketplaces as use cases.

eHealth-as-a-Service (eHaaS) : towards universal stakeholder engagement

With the introduction of the Personally Controlled Health Record (PCEHR), the Australian public is being asked to accept greater responsibility for their healthcare by taking an active role in the management of personal health information. Although well designed, constructed and intentioned, policy and privacy concerns have resulted in an eHealth model that may impact future health sharing requirements. Hence, as a case study for a consumer eHealth initative in the Australian context, eHealth-as-a-Service (eHaaS) serves as a disruptive step in in the aggregation and transformation of health information for use as real-world knowledge. The strategic value of extending the community Health Record Bank (HRB) model lies in the ability to automatically draw on a multitude of relevant data repositories and sources to create a single source of the truth and to engage market forces to create financial sustainability. The opportunity to transform the beleaguered Australian PCEHR into a realisable and sustainable technology consumption model for patient safety is explored. Moreover, the current clerical focus of healthcare practitioners acting in the role of de facto record keepers is renegotiated to establish a shared knowledge creation landscape of action for safer patient interventions. To achieve this potential however requires a platform that will facilitate efficient and trusted unification of all health information available in real-time across the continuum of care. eHaaS provides a sustainable environment and encouragement to realise this potential.

Architecture for service profiling

Service oriented architecture is gaining momentum. However, in order to be successful, the proper and up-to-date description of services is required. Such a description may be provided by service profiling mechanisms, such as one presented in this article. Service profile can be defined as an up-to-date description of a subset of non-functional properties of a service. It allows for service comparison on the basis of non-functional parameters, and choosing the service which is most suited to the needs of a user. In this article the notion of a service profile along with service profiling mechanism is presented as well as the architecture of a profiling system. © 2006 IEEE.

Failure-Oblivious Computing and Boundless Memory Blocks

Memory errors are a common cause of incorrect software execution and security vulnerabilities. We have developed two new techniques that help software continue to execute successfully through memory errors: failure-oblivious computing and boundless memory blocks. The foundation of both techniques is a compiler that generates code that checks accesses via pointers to detect out of bounds accesses. Instead of terminating or throwing an exception, the generated code takes another action that keeps the program executing without memory corruption. Failure-oblivious code simply discards invalid writes and manufactures values to return for invalid reads, enabling the program to continue its normal execution path. Code that implements boundless memory blocks stores invalid writes away in a hash table to return as the values for corresponding out of bounds reads. he net effect is to (conceptually) give each allocated memory block unbounded size and to eliminate out of bounds accesses as a programming error. We have implemented both techniques and acquired several widely used open source servers (Apache, Sendmail, Pine, Mutt, and Midnight Commander).With standard compilers, all of these servers are vulnerable to buffer overflow attacks as documented at security tracking web sites. Both failure-oblivious computing and boundless memory blocks eliminate these security vulnerabilities (as well as other memory errors). Our results show that our compiler enables the servers to execute successfully through buffer overflow attacks to continue to correctly service user requests without security vulnerabilities.

Cloud computing in e-science: research challenges and opportunities

SOA (Service Oriented Architecture), workflow, the Semantic Web, and Grid computing are key enabling information technologies in the development of increasingly sophisticated e-Science infrastructures and application platforms. While the emergence of Cloud computing as a new computing paradigm has provided new directions and opportunities for e-Science infrastructure development, it also presents some challenges. Scientific research is increasingly finding that it is difficult to handle “big data” using traditional data processing techniques. Such challenges demonstrate the need for a comprehensive analysis on using the above mentioned informatics techniques to develop appropriate e-Science infrastructure and platforms in the context of Cloud computing. This survey paper describes recent research advances in applying informatics techniques to facilitate scientific research particularly from the Cloud computing perspective. Our particular contributions include identifying associated research challenges and opportunities, presenting lessons learned, and describing our future vision for applying Cloud computing to e-Science. We believe our research findings can help indicate the future trend of e-Science, and can inform funding and research directions in how to more appropriately employ computing technologies in scientific research. We point out the open research issues hoping to spark new development and innovation in the e-Science field.

A reputation-based grid information service

In a large-scale wide-area system such as the Grid, trust is a prime concern. The current generation of grid information services lack the ability to determine how trustworthy a particular grid service provider or grid customer is likely to be. In this paper, we propose a grid information service with reputation management facility and its underlying algorithm for computing and managing reputation in service-oriented grid computing. Our reputation management service is based on the concept of dynamic trust and reputation adaptation based on community experiences. The working model and functionality offered by the proposed reputation management service is discussed.