SOA关键型系统QoS可感知的服务动态实时组合策略

针对运行于开放、不确定环境下SOA架构的多使命复杂关键型系统,提出了一个QoS可感知的服务动态组合体系结构及启发式服务实时组合算法,用于满足具有严格QoS限制的复杂用户需求。利用所提出的体系结构可以在线执行服务组合,大大提高了SOA关键型系统的灵活性。通过启发式算法解决了以往服务组合算法时间复杂度的NP难题,最后通过一组实验证明该启发式算法的实时性和具体优化结果。     

基于SOA的策略服务平台设计与实现

本文通过分析现有基于策略的网络管理系统架构,结合SOA思想设计并实现基于SOA的策略服务平台,并将该平台应用到基于策略的异构网络管理系统中,为其提供策略服务,实现了对异构网络资源的高效自治管理。     

An effective adaptive adjustment method for service composition exception handling in cloud manufacturing

Journal of Intelligent Manufacturing - With the increasing market features of globalization, service and customization, the way manufacturers conduct manufacturing business is changing. Under this...     

基于SOA的分布式服务供应链信息共享平台研究与实践*

以SOA理论体系为出发点,提出了基于企业服务总线（enterprise service bus,ESB）的分布式服务供应链信息共享平台的体系结构,并分析了该信息共享平台建设的生命周期。进一步采用案例分析的研究方法,以企业信息系统设计项目与IBM高校合作项目为例子,探讨了分布式服务供应链信息共享平台的服务建模过程,并设计和开发了一个分布式服务供应链信息共享平台。     

基于SOA体系的企业系统协同平台的研究和应用

在分析企业现有业务系统协同工作需求的基础上,基于对SOA体系的研究,针对各异构系统在业务和流程交互、数据集成、业务集成等方面的特点,提出了基于SOA技术体系的企业系统协同工作平台建设方案,并从协同工作平台技术架构、功能设计、关键技术等方面进行研究,解决了现有业务系统在统一协同工作环境,统一系统技术体系、基础数据标准和规范等方面的需求.     

An effective dynamic service composition reconfiguration approach when service exceptions occur in real-life cloud manufacturing

Cloud Manufacturing Service Composition (CMSC), as one of the key issues of Cloud Manufacturing (CMfg), has already attracted much attention. Existing researches on CMSC mainly focus on the optimization efficiency in ideal conditions, while scarcely focus on how to efficiently reconfigure CMSC when service exceptions occur. Uncertain service exceptions often occur during CMSC's execution in real-life CMfg. Thus, it is an urgent issue to perform an adjustment for CMSC to continue to complete the processing task. Besides, some practical constraints are non-negligible in real-world CMfg. Thus, it is necessary to consider them when reconfiguring CMSC. To bridge these gaps, this paper proposes a dynamic service composition reconfiguration model when service exceptions occur under practical constraints (DSCRWECPC). This model redefines optimization objectives, including machining quality, service quality, and cost. Besides, DSCRWECPC considers service exceptions, the cloud manufacturing service occupancy time constraint, the strict time constraint of original CMSC, and dynamic service quality change as its practical constraints. To solve this model, this paper proposes a service composition reconfiguration algorithm (SCRIHHO) based on the strengthened Harris Hawks Optimizer (HHO). Finally, to certify SCRIHHO's performance, this paper conducts numerical experiments and the case application to perform comparisons between SCRIHHO and other algorithms (Particle Swarm Optimization (PSO) and Grey Wolf Optimizer (GWO)). Results showed SCRIHHO in this paper is superior to PSO, GWO when tackling the practical DSCRWECPC in CMfg.     

Towards efficiency of QoS-driven semantic web service composition for large-scale service-oriented systems

Quality-of-Service (QoS) performance guarantee for service-oriented systems (SOS) has become a critical problem. With the increasing number of offered services comes the challenge of efficiently building large-scale SOS to meet the required QoS criteria. Optimization of QoS-driven semantic Web service composition is known to be NP-hard. We address the efficiency issue by developing a polynomial time algorithm (QDA) for shortest sequence composition. We use dynamic programming to find service candidates for each execution. When all the services are searched, we use a depth-first trace back to derive the execution plan. We have tested our approach under Web-scale demands 20,000 services and 150,000 semantic concepts. In comparison with existing approaches, our experimental results show that QDA can be used to solve large-scale service composition problem effectively and efficiently with QoS guarantee.     

Indeterminacy-aware service selection for reliable service composition

With the development of Internet and Web service technology, Web service composition has been an effective way to construct software applications; service selection is the crucial element in the composition process. However, the existing selection methods mostly generate static plans since they neglect the inherent stochastic and dynamic nature of Web services. As a result, Web service composition often inevitably terminates with failure. An indeterminacy-aware service selection algorithmbased on an improved Markov decision process (IMDP) has been designed for reliable service composition, but it suffers from higher computation complexity. Therefore, an efficient method is proposed, which can reduce the computation cost by converting the service selection problem based on IMDP into solving a nonhomogeneous linear equation set. Experimental results demonstrate the success rate of service composition has been improved greatly, whilst also reducing computation cost.     

A geometric model for an effective rescheduling after reducing service in public transportation systems

Railway systems in metropolitan areas carry a high density of traffic daily, heterogeneously distributed, and exposed to the negative consequences derived from service disruptions. An interesting topic in the literature is to obtain performance protocols in the presence of contingencies which can affect the system operation, avoiding the propagation of perturbation and minimizing its consequences. The objective of this paper is to assess the decision of rescheduling the train service, reducing the current supply along one transportation line in order to reinforce the service of another line, exploited by the same public operator, which has suffered an incidence or emergency. A methodology, based on a geometric representation of solutions which allows the use of discrete optimization techniques, is developed in order to attend to the underlying demand with efficiency criteria in this context of unexpected incidents.     

Toward self-organizing service communities

This paper discusses a framework in which catalog service communities are built, linked for interaction, and constantly monitored and adapted over time. A catalog service community (represented as a peer node in a peer-to-peer network) in our system can be viewed as domain specific data integration mediators representing the domain knowledge and the registry information. The query routing among communities is performed to identify a set of data sources that are relevant to answering a given query. The system monitors the interactions between the communities to discover patterns that may lead to restructuring of the network (e.g., irrelevant peers removed, new relationships created, etc.).     

Toward high-precision service retrieval

Online repositories are increasingly called on to provide access to services that describe or provide useful behaviors. Existing techniques for finding services offer low retrieval precision, returning many irrelevant matches. We introduce a novel service retrieval approach that captures service semantics using process models, and applies a pattern-matching algorithm to find the services with the behavior the user wants. Evaluations suggest that process-based queries offer substantially greater retrieval precision than existing approaches and scale well with the number of services being accessed.     

A flexible time-triggered service for real-time CORBA

This paper presents a new service for CORBA applications that orchestrates the timely execution of the tasks of a distributed real-time system in a flexible way. It follows the CORBA philosophy of complementing the CORBA standard with additional services that solve specific problems and facilitate using CORBA in complex applications. The service has been designed for highly coupled applications that execute over LANs. It provides a synchronous framework to synchronize distributed applications that is open to accepting and removing components on-line, with reduced impact on the application timing. It also provides the flexibility to use different distributed scheduling policies that can override the local operating systems schedulers. This paper describes the service architecture and implementation as well as its best-case performance on low computing power hardware with the QNX OS and connected to a switched Ethernet network. Finally the usage and of the service is illustrated with one case study: the synchronization of several robots in a welding process.     

Scheduling for reactive real-time systems

In designing Chinook, a hardware-software cosynthesis system for reactive real-time controllers, the impact of timing constraints on software scheduling has been a central concern. By dividing constraints into two levels, corresponding to low-level interactions with device interfaces and high-level real-time response and rate requirements, we have developed solutions tailored to each aspect. These scheduling techniques enable Chinook to map a high-level specification onto a specified collection of processors and peripheral devices while respecting performance requirements     

Requirements-based monitors for real-time systems

Before designing safety- or mission-critical real-time systems, a specification of the required behavior of the system should be produced and reviewed by domain experts. After the system has been implemented, it should be thoroughly tested to ensure that it behaves correctly. This is best done using a monitor, a system that observes the behavior of a target system and reports if that behavior is consistent with the requirements. Such a monitor can be used both as an oracle during testing and as a supervisor during operation. Monitors should be based on the documented requirements of the system. If the target system is required to monitor or control real-valued quantities, then the requirements, which are expressed in terms of the monitored and controlled quantities, will allow a range of behaviors to account for errors and imprecision in observation and control of these quantities. Even if the controlled variables are discrete valued, the requirements must specify the timing tolerance. Because of the limitations of the devices used by the monitor to observe the environmental quantities, there is unavoidable potential for false reports, both negative and positive, This paper discusses design of monitors for real-time systems, and examines the conditions under which a monitor will produce false reports. We describe the conclusions that can be drawn when using a monitor to observe system behavior     

Conformance testing for real-time systems

We propose a new framework for black-box conformance testing of real-time systems. The framework is based on the model of partially-observable, non-deterministic timed automata. We argue that partial observability and non-determinism are essential features for ease of modeling, expressiveness and implementability. The framework allows the user to define, through appropriate modeling, assumptions on the environment of the system under test (SUT) as well as on the interface between the tester and the SUT. We consider two types of tests: analog-clock tests and digital-clock tests. Our algorithm for generating analog-clock tests is based on an on-the-fly determinization of the specification automaton during the execution of the test, which in turn relies on reachability computations. The latter can sometimes be costly, thus problematic, since the tester must quickly react to the actions of the system under test. Therefore, we provide techniques which allow analog-clock testers to be represented as deterministic timed automata, thus minimizing the reaction time to a simple state jump. We also provide algorithms for static or on-the-fly generation of digital-clock tests. These tests measure time only with finite-precision digital clocks, another essential condition for implementability. We also propose a technique for location, edge and state coverage of the specification, by reducing the problem to covering a symbolic reachability graph. This avoids having to generate too many tests. We report on a prototype tool called and two case studies: a lighting device and the Bounded Retransmission Protocol. Experimental results obtained by applying on the Bounded Retransmission Protocol show that only a few tests suffice to cover thousands of reachable symbolic states in the specification.     

Scheduling for embedded real-time systems

The authors review several approaches to control-oriented and dataflow-oriented software scheduling to determine whether a given technique can satisfy deadlines, throughput, and other constraints for embedded real-time systems     

Concurrent engineering for real-time systems

The Incremental Prototyping Technology for Embedded Real-Time Systems (Iptes) project, which is part of ESPRIT II, is described. The goal of the project is to develop methodologies and tools for the distributed prototyping of real-time systems. The work concentrates on two areas of support for concurrent engineering: adapting graphical-animation techniques to real-time-system development and creating a mechanism for propagating changes within and between tasks     

Network invariants for real-time systems

We extend the approach of model checking parameterized networks of processes by means of network invariants to the setting of real-time systems. We introduce timed transition structures (which are similar in spirit to timed automata) and define a notion of abstraction that is safe with respect to linear temporal properties. We strengthen the notion of abstraction to allow a finite system, then called network invariant, to be an abstraction of networks of real-time systems. In general the problem of checking abstraction of real-time systems is undecidable. Hence, we provide sufficient criteria, which can be checked automatically, to conclude that one system is an abstraction of a concrete one. Our method is based on timed superposition and discretization of timed systems. We exemplify our approach by proving mutual exclusion of a simple protocol inspired by Fischer’s protocol, using the model checker TLV. Part of this work was done during O. Grinchtein’s stay at Weizmann Institute. This author was supported by the European Research Training Network “Games”.