Network-based social coordination of business processes

This paper presents a social coordination approach that addresses the issue of conflicts over resources during business process execution. A business process consists of tasks that persons and/or machines execute. The resources, that business processes require at run-time, are sometimes limited and/or not-renewable. The approach uses a set of social relations that connect tasks/persons/machines together. These relations are the basis of developing specialized networks that capture the interactions during business process execution and are used to recommend corrective actions when conflicts over resources occur. These actions are dependent on the properties of tasks, persons and machines properties which referred to as transactional, activity, and operational, respectively. A system that demonstrates the approach is also discussed.     

基于TC-Net的工作流模型研究

时间要素作为工作流管理的重要部分,是影响企业业务流程部署实施的关键因素。基于工作流中任务具有时间限制的特点,分析任务的时间要素,抽象出任务的形式化描述,定量计算两个连续任务执行的最大时间约束,提出可控时间约束Petri网模型（Time Constraint-Net,TC-Net）。该模型在任务节点中添加时间信息,从任务开始执行时间到任务的执行结束时间及最大约束时间,提高任务时间信息描述精度;利用TC-Net模型表示工作流过程中各项任务,基于任务间顺序、同步和并行关系的传递模型,细化实际业务流程中分析粒度。应用TC-Net模型进行实例分析,实验结果表明该工作流建模方法对时间违反而导致违规操作具有高敏感性,解决了单个任务违规和流程周期不合理两类问题,实现业务过程的管理和监控。     

Communication constraints in the average consensus problem

The interrelationship between control and communication theory is becoming of fundamental importance in many distributed control systems, such as the coordination of a team of autonomous agents. In such a problem, communication constraints impose limits on the achievable control performance. We consider as instance of coordination the consensus problem. The aim of the paper is to characterize the relationship between the amount of information exchanged by the agents and the rate of convergence to the consensus. We show that time-invariant communication networks with circulant symmetries yield slow convergence if the amount of information exchanged by the agents does not scale well with their number. On the other hand, we show that randomly time-varying communication networks allow very fast convergence rates. We also show that by adding logarithmic quantized data links to time-invariant networks with symmetries, control performance significantly improves with little growth of the required communication effort.     

Execution system for distributed business processes in a virtual enterprise

New cooperative approaches for manufacturing and service industries, as represented by the virtual enterprise paradigm, are enabled by the recent advances in communication technologies, computer networks, and logistics. The implantation of this paradigm requires the design and development of a flexible execution environment to support the distributed business processes that materialize the cooperation in a network of enterprises. A configurable architecture for such execution system is proposed focusing the support for multi-level process coordination. A set of examples to illustrate the adopted concepts and developed tools are discussed.     

状态驱动的可执行业务流程模型的设计与实现

在企业间的流程协同过程中,为了使企业的业务规则管理更灵活,防止企业私有的业务规则暴露给其他企业,并有效地监控流程的执行过程,将业务规则库和Web服务有机地整合,构建状态驱动的可执行业务流程模型（SEBPM）。通过定义抽象业务流和扩展的业务规则,得出业务规则和过程流之间的耦合策略。给出一个SEBPM的具体应用实例。     

A reference model of virtual service production networks

Virtual organisation of collaborative networks frequently demands for information and communication technology to support coordination of cross-organisational business process chains. Service-oriented software technologies provide promising means to regulate and enforce coordination of cross-organisational software service interactions but miss organisational abstractions and methodology. This paper proposes a conceptual reference model of collaborative network coordination that satisfies flexibility and agility requirements of virtual organisation by building on common software service abstractions and lifecycle methodology. In particular, the model focuses collaborative service networks and introduces the concept of virtual business service that represents business service processes as software service abstractions and supports flexible regulation and agile enforcement of their coordination by means of software service lifecycle methodology. For demonstration and evaluation purpose, we present a case study of service-oriented systems analysis for virtual organisation of a collaborative e-science network that adopts our conceptual reference model.     

Exception handling for copyless messaging

Copyless messaging is a communication paradigm in which only pointers to messages are exchanged between sender and receiver processes. Because of its intrinsically low overhead, copyless messaging is suitable for the efficient implementation of communication-intensive software systems where processes have access to a shared address space. Unfortunately, the very nature of the paradigm fosters the proliferation of programming errors due to the explicit use of pointers and to the sharing of data. In this paper we study a type discipline for copyless messaging that, together with some minimal support from the runtime system, is able to guarantee the absence of communication errors, memory faults, and memory leaks in the presence of exceptions. To formalize the semantics of processes we draw inspiration from software transactional memories: in our case a transaction is a process that is meant to accomplish some exchange of messages and that should either be executed completely, or should have no observable effect if aborted by an exception.     

Timed Specification For Web Services Compatibility Analysis

Web services are becoming one of the main technologies for designing and building complex inter-enterprise business applications. Usually, a business application cannot be fulfilled by one Web service but by coordinating a set of them. In particular, to perform a coordination, one of the important investigations is the compatibility analysis. Two Web services are said compatible if they can interact correctly. In the literature, the proposed frameworks for the services compatibility checking rely on the supported sequences of messages. The interaction of services depends also on other properties, such that the exchanged data flow. Thus, considering only supported sequences of messages seems to be insufficient. Other properties on which the services interaction can rely on, are the temporal constraints. In this paper, we focus our interest on the compatibility analysis of Web services regarding their (1) supported sequences of messages, (2) the exchanged data flow, (3) constraints related to the exchanged data flow and (4) the temporal requirements. Based on these properties, we study three compatibility classes: (i) absolute compatibility, (ii) likely compatibility and (iii) absolute incompatibility.     

Extending the reach of business processes

A business process is a systematic set of activities by which an enterprise conducts its affairs. Various technologies-including pagers, cell phones, pocket PCs, instant messaging (IM), and the short message service (SMS)-have emerged that people can use to communicate even when they are on the move or far away. Many such devices support synchronous communication as well as proactively "pushing" messages to users. However, these devices have no mechanism to control or structure the information that users are exchanging, and they arc not integrated with business processes based on workplaces. To address these problems, we have designed and implemented PerCollab, a middleware system that facilitates structured collaboration between various communication devices for business processes and pushes tasks to users.     

Targets-Drives-Means: A declarative approach to dynamic behavior specification with higher usability

Small humanoid robots are becoming more affordable and are now used in fields such as human–robot interaction, ethics, psychology, or education. For non-roboticists, the standard paradigm for robot visual programming is based on the selection of behavioral blocks, followed by their connection using communication links. These programs provide efficient user support during the development of complex series of movements and sequential behaviors. However, implementing dynamic control remains challenging because the data flow between components to enforce control loops, object permanence, the memories of object positions, odometry, and finite state machines has to be organized by the users. In this study, we develop a new programming paradigm, Targets-Drives-Means, which is suitable for the specification of dynamic robotic tasks. In this proposed approach, programming is based on the declarative association of reusable dynamic components. A central memory organizes the information flows automatically and issues related to dynamic control are solved by processes that remain hidden from the end users. The proposed approach has advantages during the implementation of dynamic behaviors, but it requires that users stop conceiving robotic tasks as the execution of a sequence of actions. Instead, users are required to organize their programs as collections of behaviors that run in parallel and compete for activation. This might be considered non-intuitive but we also report the positive outcomes of a usability experiment, which evaluated the accessibility of the proposed approach.     

Performance bounds for concurrent software with rendezvous

Synchronous message-passing communication, or rendezvous, occurring between software tasks can have a significant effect on system performance. The rendezvous style of communication is coming into wider use in programming languages and operating systems for parallel and distributed environments. Understanding the performance implications of this style of inter-task communication is becoming a matter of practical importance. The dual nature of a task which acts both like a customer as well as a server, makes the performance analysis of rendezvous-based multitasking systems quite different from the analysis of the other queueing systems with known results. This research focuses on rendezvous-based systems in which the execution behavior of the software has a nondeterministic component of a very general nature which may for example be the manifestation of a data dependent behavior. Based on a model called the Stochastic Rendezvous Network the computation of bounds on task throughputs for multitasking systems characterized by rendezvous style communication is presented. Although the behavior of tasks is called stochastic, it is very general and the results are valid for general distributions of computation times and the number of messages generated by tasks. The inter-relationship among task throughputs, however, makes it difficult to extract the bounds in closed analytic form. The notion of a feasible throughput region which encloses the set of feasible tasks throughputs and captures the inter-relationship among the behavior of tasks is introduced. Variations of this basic bounding approach that are useful in the context of different types of multitasking systems are considered in the article. For example, a novel technique based on interval arithmetic is proposed for the computation of numerical values for the bounds. The applicability of the bounds and their tightness are analyzed through case studies. Issues such as the inter-relationship between the software architecture and system performance, and the effect of processor contention on the performance bounds are discussed.     

Real-time communication in multihop networks

Communication in real-time systems has to be predictable, because unpredictable delays in the delivery of messages can adversely affect the execution of tasks dependent on these messages. We develop a scheme for providing predictable interprocess communication in real-time systems with (partially connected) point-to-point interconnection networks, which provide guarantees on the maximum delivery time for messages. This scheme is based on the concept of a real-time channel, a unidirectional connection between source and destination. A real-time channel has parameters that describe the performance requirements of the source-destination communication, e.g., from a sensor station to a control site. Once such a channel is established, the communications subsystem guarantees that these performance requirements will be met. We concentrate on methods to compute guarantees for the delivery time of messages belonging to real-time channels. We also address problems associated with allocating buffers for these messages and develop a scheme that preserves delivery time guarantees     

Detecting proximity events in sensor networks

Sensor networks are often used to perform monitoring tasks, such as animal and vehicle tracking, or the surveillance of enemy forces in military applications. In this paper we introduce the concept of proximity queries, which allow us to report interesting events, observed by nodes in the network that lie within a certain distance from each other. An event is triggered when a user-programmable predicate is satisfied on a sensor node. We study the problem of computing proximity queries in sensor networks and propose several alternative techniques that differ in the number of messages exchanged by the nodes and the quality of the returned answers. Our solutions utilize a distributed routing index, maintained by the nodes in the network, that is dynamically updated as new observations are obtained by the nodes. This distributed index allows us to efficiently process multiple proximity queries involving several different event types within a fraction of the cost that a straightforward evaluation requires. We present an extensive experimental study to show the benefits of our techniques under different scenarios using both synthetic and real data sets. Our results demonstrate that our algorithms scale better and require significantly fewer messages compared to a straightforward execution of the queries.     

具有监控能力的Agent模型

在大信息量、动态环境下企业软件系统对业务流程的监控和自动管理的需求越来越大.本文把Agent技术引入业务流程的监控和管理,在基本的BDI模型基础上加入能力组件的概念,提出一种具有监控能力的BDIC Agent模型,以具体应用背景中的实例说明了该模型中监控能力的分类.该模型已在一个客户服务系统（CSM）中成功应用,说明所提出的Agent模型具有良好的可重用性和可定制性,适合对企业软件系统中的业务流程进行监控和管理.     

Tlib—a library to support programming with hierarchical multi-processor tasks

The paper considers the modular programming with hierarchically structured multi-processor tasks on top of SPMD tasks for distributed memory machines. The parallel execution requires a corresponding decomposition of the set of processors into a hierarchical group structure onto which the tasks are mapped. The result is a multi-level group SPMD computation model with varying processor group structures. The advantage of this kind of mixed task and data parallelism is a potential to reduce the communication overhead and to increase scalability. We present a runtime library to support the coordination of hierarchically structured multi-processor tasks. The library exploits an extended parallel group SPMD programming model and manages the entire task execution including the dynamic hierarchy of processor groups. The library is built on top of MPI, has an easy-to-use interface, and leads to only a marginal overhead while allowing static planning and dynamic restructuring.     

Measures and mechanisms for process monitoring in evolving business networks

The literature on monitoring of cross-organizational processes, executed within business networks, considers monitoring only in the network formation phase, since network establishment determines what can be monitored during process execution. In particular, the impact of evolution in such networks on monitoring is not considered. When a business network evolves, e.g. contracts are introduced, updated, or dropped, or actors join or leave the network, the monitoring requirements of the network actors change as well. As a result, the monitorability of processes in the network may be disrupted. This paper proposes a framework to solve the problem of preserving the monitorability of processes in an evolving business network. We first propose a formal model of business networks, contracts, and monitoring requirements. Then, we model network evolution and the mechanisms to preserve the monitorability of the processes in the network for different types of evolution. In particular, the preservation of monitorability requires the actors in the network to take appropriate actions in case of dependencies between already established contracts, and update their monitoring infrastructure to satisfy the new monitoring requirements introduced by evolution. We also define a set of metrics that can be used for supporting decisions regarding the potential evolution of a business network. A case study in healthcare and the discussion of a prototype implementation show the applicability of our framework in real-world scenarios.     

基于补偿业务生成图的组合服务异常处理方法研究

为提高组合Web服务执行的一致性、可靠性,提出一种基于补偿业务生成图的组合服务异常处理方法.基于业务流程中任务间补偿依赖关系,讨论了补偿业务生成图的自动生成问题.重点讨论了补偿任务、补偿目标和服务转让应用模式,并相应地介绍了支持框架和相关技术.在此基础上设计了补偿依赖关系、补偿业务生成图的自动生成及组合服务执行过程中异常处理算法.当业务流程出现异常采取向前或向后恢复处理时,该方法在保证补偿实现的同时,兼顾补偿服务不存在或补偿服务代价过高的问题,提高了业务流程执行过程中的自动化水平和自适应能力.仿真结果证实,该方法保证了异常发生时组合服务执行的可靠性和一致性.     

Hierarchical time-extended Petri nets (H-EPNs) based erroridentification and recovery for multilevel systems

In this paper, hierarchical time-extended Petri nets (H-EPNs), an extended Petri net based modeling and analysis tool, are used to derive the coordination level model of hierarchically decomposable systems, viewed from a three-level hierarchical structure of organization, coordination and execution of tasks. A two-layer (vertical) coordination level framework, consisting of the dispatcher/analyzer and the H-EPN controller is presented. A detailed two sub-level (horizontal) H-EPN controller model is derived to model system operations (including system soft failures). Error classification based on the interaction between the various system coordinators is derived from the H-EPN model. The H-EPN approach preserves multi-resolutional system details as well as effective communication flows between the various subsystems. A simple example illustrates the proposed approach. The important H-EPN properties of boundedness, safeness and reversibility are verified.     

基于进程投机并行的运行时系统设计与优化

投机并行化是解决遗留串行代码并行化的重要技术,但以往投机并行化运行时系统面临着诸多的性能问题,如任务分配不均衡、通信频繁、冲突代价高,以及进程启动,结柬频繁而导致开销过高等。为此,提出一种基于进程实现的投机并行化运行时系统。采用隐式单程序多数据的并行任务划分和执行模式。通过实现重甩进程的投机任务调度策略和委托正确性检查技术,降低投机进程启动/结束和通信的开销,提高投机进程的利用率,同时利用守护进程与投机进程协同执行的方式,确保在投机进程出现异常情况时程序也能正确执行。实验结果表明,该基于进程实现的投机运行时系统比同类型系统的性能提高231%。     

一种基于负载均衡性的网格任务调度算法

针对二分图匹配算法在任务之间存在时序关系时无法进行有效调度以及EFT算法没有充分考虑各处理机性能及网络通信状况的问题,提出基于二分图匹配的改进ETF算法。该算法综合考虑任务之间的时序关系、处理机的性能、处理机之间的通信情况及已处理任务的调度情况,利用二分图最佳匹配思想对局部任务进行调度。实验表明该算法具有较小的调度长度和较好的负载均衡性。