Jun-Jang Jeng

Toward a Smart Cyber-Physical Space: A Context-Sensitive Resource-Explicit Service Model

Cyber-Physical Systems (CPSs) are combinations of physical devices controlled by software systems to accomplish specified tasks under stringent real-time and physical resource constraints. The major benefit of these systems lies in their potentially positive impacts on real world systems by enabling high dependability assurance. However, a key challenge is to determine not only correct but also cost-effective dynamic operation of all physical devices in the system in the context of real world constraints.In this paper, we present a novel context-sensitive resource-explicit service model and develop the corresponding composition formalisms to help automate the composition process under real-time constraints as well as under various physical resource constraints. The approach is illustrated using an emergency response system.

Toward effective service composition for real-time SOA-based systems

Many application domains are increasingly leveraging service-oriented architecture (SOA) techniques to facilitate rapid system deployment. Many of these applications are time-critical and, hence, real-time assurance is an essential step in the service composition process. However, there are gaps in existing service composition techniques for real-time systems. First, admission control is an essential technique to assure the time bound for service execution, but most of the service composition techniques for real-time systems do not take admission control into account. A service may be selected for a workflow during the composition phase, but then during the grounding phase, the concrete service may not be able to admit the workload. Thus, the entire composition process may have to be repeated. Second, communication time is an important factor in real-time SOA, but most of the existing works do not consider how to obtain the communication latencies between services during the composition phase. It is clear that maintaining a full table of communication latencies for all pairs of services is infeasible. Obtaining communication latencies between candidate services during the composition phase can also be costly, since many candidate services may not be used for grounding. Thus, some mechanism is needed for estimating the communication latency for composite services. In this paper, we propose a three-phase composition approach to address the above issues. In this approach, we first use a highly efficient but moderately accurate algorithm to eliminate most of the candidate compositions based on estimated communication latencies and assured service response latency. Then, a more accurate timing prediction is performed on a small number of selected compositions in the second phase based on confirmed admission and actual communication latency. In the third phase, specific concrete services are selected for grounding, and admissions are actually performed. The approach is scalable and can effectively achieve service composition for satisfying real-time requirements. Experimental studies show that the three-phase approach does improve the effectiveness and time for service composition in SOA real-time systems. In order to support the new composition approach, it is necessary to effectively specify the needed information. In this paper, we also present the specification model for timing-related information and the extension of OWL-S to support this specification model.

System Dynamics Modeling for SOA Project Management

Service-Oriented Architecture (SOA) has the potential to vastly improve ITs efficiency. But to implement one at an organization, enterprises need more than just technical know-how: the leadership team has to be skilled in management as well. Especially, SOA implies different emphasis of project management. This paper describes in brief the use of system dynamics models for managing large scale SOA projects. System dynamics is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems. In fact it has been used to address practically every sort of feedback system including project management. In this paper, we will present a framework of managing SOA projects and show how system dynamics model can be used to enhance the effectiveness and agility of SOA project management. A general SOA project lifecycle is presented and two examples are used to illustrate the needs and effectiveness of adopting quantified simulation method such as system dynamics into large-scale SOA projects.

Authoring Tool for Business Performance Monitoring and Control

To monitor and warrant the performance of concerned business operations, formal representation for business performance models are needed so business analysts can describe what they expect from business service providers. This paper proposes a metamodel and an authoring tool for describing business performance for business services in the context of SOA. A business performance model explicitly captures the intentions of the consumers of the target business services. The authoring tool simplifies the modeling of the performance models. With our proposed mechanism, computational models for business performance management are generated. The separation of concerns in terms of business performance models and computational models allows for seamless transitions from business level performance models to runtime.

Service Composition for Real-Time Assurance

Service oriented architecture (SOA) has become a popular paradigm for software development in many application domains, including real-time applications. Timing analysis is a critical issue which can guide service composition to best satisfy the real time requirements of the composed system. However, existing timing analysis works do not sufficiently address some important issues. For example, admission control is an important technique for real time assurance, but most of the timing analysis techniques do not take admission control into account and, hence, may result in unrealizable decisions. Also, communication time is an important factor in real-time assurance, but most of the works do not provide clear approaches in dealing with communication time analysis. In this paper, we propose a timing specification model and analysis techniques for real-time service-oriented systems. In the specification model, a thorough consideration of all information required for timing analysis is discussed. For timing analysis, we consider the service time softly guaranteed by the admission control policy as well as estimated communication cost to reach more accurate timing estimates. Also, to avoid the analysis overhead in large-scale SOA systems, we propose a three-phase approach. In this approach, we first use a highly efficient but moderately accurate algorithm to eliminate most of the candidate compositions. More accurate timing prediction is performed on a small number of selected compositions in the second phase. In the third phase, specific concrete services are selected and admissions are performed to finalize the composition and service grounding. The approach is scalable and can effectively achieve service composition for real time requirement satisfaction.

PACTS: A Service Oriented Architecture for Real-Time Peer-Assisted Content Delivery Service

Compared with the traditional client/server streaming model, peer-assisted video streaming has been shown to provide better scalability with lower infrastructure cost. In this paper, we describe how peer-assisted video streaming can be implemented through real-time service oriented architecture. Our architecture, dubbed PACTS, is composed of 5 distinct service components: directory service, content service, peer download service, peer upload service and rate composition service. PACTS is designed to meet the specific QoS requirements of different users, entered through a simple Web interface. It also provides a distributed implementation of the content and peer directory services for effectively handling flash crowd situations, when a large number of users join during a very short period of time. We discuss the functionalities of the main PACTS services and specify the workflow of how these services work together to deliver real-time streaming services leveraging the benefits of peer to peer technology. By organizing elements of traditional video streaming and peer to peer computing into loosely-coupled composable middleware services and distributing them among participating entities, PACTS enables high-quality low- cost video streaming at a large scale and in real time.

Guest editorial: special section on real-time service-oriented architecture and applications

As the paradigm service-oriented computing gains more prominence in the development of systems and commercial applications, the capability of guaranteeing service timeliness is becoming a critical feature that differentiates an enterprise from its competitors. A real-time business competes with other businesses by shortening the latencies of data, analysis, decision and execution. As such, real time serviceoriented architecture and applications (RTSOAA) elevate the traditional service-oriented computing approach to the next level of excellence. RTSOAA presents a new set of emerging issues and challenges that are expected to be identified, resolved by the service-oriented computing community. These issues cover scientific and engineering approaches to meet timing constraints and to select services and resources for optimizing the tradeoff between cost and efficiency. Moreover, there are technical and managerial issues existing for RTSOAA: modeling, infrastructure composition, coordination, planning and scheduling, choreography, deployment, configuration, monitoring and control, and governance. Last, RTSOAA has potential contribution to diverse domains such as CyberPhysical Systems, Cloud Computing, Healthcare IT, Green Computing, Large-Scale Analytics, Workload Optimization, Scientific Computing, and so on. The IEEE International Workshop of Real-Time ServiceOriented Architecture and Applications (RTSOAA) inaugurated in the historical Turku of Finland on 28 July 2009. Researchers from the diverse areas presented and debated

Design and implementation of a service oriented architecture for peer-assisted video-on-demand

Compared with the traditional client/server streaming model, peer-assisted video streaming has been shown to provide better scalability with lower infrastructure cost. In this paper, we describe how peer-assisted video streaming can be implemented through real-time service oriented architecture. The first part of the paper presents an overall design of the Peer-Assisted ContenT Service (PACTS). We discuss the motivation, principles and service oriented architecture of PACTS modules and specify the workflow among them. By organizing elements of traditional video streaming and peer-to-peer computing into loosely-coupled composable middleware services and distributing them among participating entities, PACTS enables high-quality low-cost video streaming at a large scale and in real time. The second part of the paper describes an implementation of PACTS using existing off-the-shelf software followed by a performance evaluation based on practical environment settings. We illustrate the challenges and our approaches in designing distributed and highly efficient algorithms. In particular, the algorithms for performing peering-selection and incentive-driven pre-fetching are studied in detail. These designs are extensively evaluated by packet-level simulations. We show that our implementation of PACTS effectively offload server’s bandwidth demand without sacrificing the service quality. This benefit is further verified in dynamic settings with system churns. The simulation results show that the incentive mechanism from our service level agreement efficiently stabilizes the server bandwidth utilization with less than 4.5% control traffic overhead.

Designing an SOA for P2P On-Demand Video Delivery

Compared with the traditional client/server streaming model, peer-assisted video streaming has been shown to provide better scalability with lower infrastructure cost. In this chapter, we describe how peer-assisted video streaming can be implemented through real-time service oriented architecture. This chapter presents an overall design of the Peer-Assisted ContenT Service (PACTS). We discuss the motivation, principles and service oriented architecture of PACTS modules and specify the workflow among them. By organizing elements of traditional video streaming and peer to peer computing into loosely-coupled composable middleware services and distributing them among participating entities, PACTS enables high-quality low-cost video streaming at a large scale and in real time. We illustrate the challenges and our approaches in designing distributed and highly efficient algorithms. In particular, the algorithms for performing peering-selection and incentive-driven pre-fetching are studied in detail. These designs are extensively evaluated by packet-level simulations which are beyond the scope of this paper. We show that our implementation of PACTS effectively offload server’s bandwidth demand without sacrificing the service quality. This benefit is further verified in dynamic settings with system churns.