Computational offloading advances the deployment of Mobile Edge Computing (MEC) in the next generation communication networks. However, the distributed nature of the mobile users and the complex applications make it challenging to schedule the tasks reasonably among multiple devices. Therefore, by leveraging the idea of Software-Defined Networking (SDN) and Service Composition (SC), we propose a Software-Defined Service Composition model (SDSC). In this model, the SDSC controller is deployed at the edge of the network and composes service in a centralized manner to reduce the latency of the task execution and the traffic on the access links by satisfying the user-specific requirement. We formulate the low latency service composition as a Constraint Satisfaction Problem (CSP) to make it a user-centric approach. With the advent of the SDN, the global view and the control of the entire network are made available to the network controller which is further leveraged by our SDSC approach. Furthermore, the service discovery and the offloading of tasks are designed for MEC environment so that the users can have a complex and robust system. Moreover, this approach performs the task execution in a distributed manner. We also define the QoS model which provides the composition rule that forms the best possible service composition at the time of need. Moreover, we have extended our SDSC model to involve the constant mobility of the mobile devices. To solve the mobility issue, we propose a mobility model and a mobility-aware QoS approach enabled in the SDSC model. The experimental simulation results demonstrate that our approach can obtain better performance than the energy saving greedy algorithm and the random offloading approach in a mobile environment.

O teste de programas concorrentes é essencial para assegurar a qualidade das atuais aplicações distribuídas/paralelas em desenvolvimento. Apesar de ser essencial, essa atividade de teste é dificilmente empregada adequadamente, devido a fatores como: alto custo de execução, grande lacuna entre desenvolvedores e resultados de pesquisas em testes para programas concorrentes e acesso às ferramentas de teste de programas concorrentes que automatizem/viabilizem o emprego do teste. Este projeto visa definir os parâmetros da atividade de teste estrutural de programas concorrentes que nortearão a composição de diferentes serviços na Web. Tais serviços dão suporte à atividade de teste estrutural de programas concorrentes, estabelecendo fronteiras claras em ferramentas de teste para os módulos relativos ao modelo de teste, aos critérios de teste, à linguagem de programação e aos paradigmas de sincronização. Desse modo, novas ferramentas de teste poderão ser construídas de maneira mais flexível, com menos custo de desenvolvimento e com mais eficácia. Tal abordagem traz como benefícios diretos: (1) facilitar a interação entre os setores da indústria, ensino e pesquisa que estejam interessados no desenvolvimento de programas concorrentes com qualidade; (2) diminuir os custos de instalação e manutenção de ferramentas de teste estrutural pelos desenvolvedores; (3) facilitar a incorporação da atividade de teste de programas concorrentes no ciclo de desenvolvimento das aplicações distribuídas e paralelas; (4) aumentar a abrangência do projeto TestPar, permitindo que novos usuários (desenvolvedores, professores e outros grupos de pesquisa) possam utilizar facilmente os conhecimentos gerados no projeto; e (5) realimentar o projeto TestPar com novas demandas qualificadas, estas advindas de novos programas concorrentes submetidos para teste. / Testing of concurrent programs is essential to ensure the quality of todays distributed/parallel applications in development. Although it is essential that testing activity is hardly properly employed, due to factors such as high cost of implementation, big gap between developers and research results in tests for competing programs and access to competing software testing tools to automate / enable the test job. This project aims to define the parameters of structural testing activity of concurrent programs that will guide the composition of different Web services. These services support the structural testing activity of concurrent programs, establishing clear boundaries in test tools for the modules related to the test model, the test criteria, the programming and synchronization paradigms language. Thus, new test tools can be built in a more flexible way, with less development cost and more effectively. Such an approach has as direct benefits: (1) facilitate interaction between industry sectors, education and research who are interested in the development of concurrent programs with quality; (2) reduce the costs of installation and maintenance of structural testing tools for developers; (3) facilitate the incorporation of testing activity of concurrent programs in the development cycle of distributed and parallel applications; (4) increase the scope of TestPar design, allowing new users (developers, teachers and other research groups) can easily use the knowledge generated in the project; and (5) feed back into the project TestPar with new demands qualified, those arising from new concurrent programs submitted for testing.

Users (or software agents) are served by multiple networked terminal devices, each of which may in turn have multiple network interfaces. This multi-homing at both ???user??? and ???device??? level presents new opportunities for mobility handling. Mobility may be handled by switching ongoing application data streams between devices, by utilising intermediary adaptation or connectivity enhancement services, or both. However this requires middleware support that is not provided by current systems. This thesis presents a set of integrated solutions to enable this kind of mobility handling, based on concept of Personal Networks (PN). Personal Networks (PN) consist of dynamic conglomerations of terminal and service devices tasked to facilitate the delivery of information to and from a single focal point, which may be a human user or software agent. This concept creates the potential to view mobility handling as a path selection problem, since there may be multiple valid terminal device and service proxy configurations that can successfully carry a given communication session from one PN to another PN. Depending on context, it may be necessary to switch between paths. To this end, this thesis proposes and evaluates a set of inter-dependent mechanisms to facilitate the discovery and use of different candidate end-to-end paths. The proposal comprises mechanisms for secure inter-device mobility using delegated cryptographic identifiers, autonomous service proxy selection and composition, and distributed resolution of cryptographic identifiers to lower layer addresses.

Process-based composition of Web services is emerging as a promising technology for the effective automation of integrated and collaborative applications. As Web services are often autonomous and heterogeneous entities, coordinating their interactions to build complex processes is a difficult, error prone, and time-consuming task. In addition, since Web services usually operate in dynamic and highly evolving environments, there is a need for supporting flexible and correct execution of integrated processes. In this thesis, we propose a Petri net-based framework for formal composition and recovery policies in service-based business processes. We first propose an algebra for composing Web services. The formal semantics of this algebra is expressed in terms of Petri nets. The use of a formal model allows the effective verification and analysis of properties, both within a service, such as termination and absence of deadlock, and between services, such as behavioral equivalences. We also develop a top down approach for the correct (e.g., absence of deadlock and termination) composition of complex business processes. The approach defines a set of refinement operators that guarantee correctness of the resulting business process nets at design time. We then introduce Self-Adaptive Recovery Net (SARN), an extended Petri net model for specifying exceptional behavior in business processes. SARN adapts the structure of the underlying Petri net at run time to handle exceptions while keeping the Petri net design simple and easy. The proposed framework caters for the specification of high-level recovery policies that are incorporated either with a single task or a set of tasks, called a recovery region. Finally, we propose a pattern-based approach to dynamically restructure SARN. These patterns capture the ways past exceptions have been dealt with. The objective is to continuously restructure recovery regions within the SARN model to minimize the impact of exception handling. To illustrate the viability of the proposed composition and exception handling techniques, we have developed HiWorD (HIerarchical WORkflow Designer), a hierarchical Petri net-based business process modeling and simulation tool.

Web services composition is emerging as a promising technology for the effective automation of application-to-application collaborations. The application integration problems have been subject of much research in the past years. However, with growth in importance of business process automation and highly dynamic nature of the Internet, this research has taken on a new significance and importance. Adequate solutions to this problem will be very important to make enterprise systems more flexible, robust and usable in the future. In this dissertation, we present a novel approach for the declarative definition and scalable orchestration of composite Web services in large, autonomous, heterogeneous, and dynamic environments. We first propose a composition model for composing Web services in a personalized and adaptive manner. We model composite Web services based on statecharts. To cater for large amounts of dynamic Web services, we use the concept of service community that groups services together and is responsible for the runtime selection of services against user's preferences. We use the concept of process schema that specific users can adjust with their personal preferences. A set of exception handling policies can be specified to proactively react to runtime exceptions. We then propose a tuple space based service orchestration model for distributed, self-managed composite services execution. We introduce the concept of execution controller that is associated with a service and is responsible for monitoring and controlling service executions. The knowledge required by a controller is statically extracted from the specification of personalized composite services. We also present techniques for robust Web services provisioning. The techniques presented in this dissertation are implemented in Self-Serv, a prototype that provides a set of tools for Web service composition and execution. Finally, we conduct an extensive usability and performance study of the proposed techniques. The experimental results reveal that our system i) provides an efficient support for specifying, deploying, and accessing composite services; ii) is more scalable and outperforms the centralized approach when the exchanged messages become bigger; and iii) is more robust and adaptive in highly dynamic environments.

No description available.

Content delivery through service overlay networks has gained popularity due to the overlays’ abilities to provide effective and reliable services. Inefficiencies of one-to-one matching of user requirements to a single service have given rise to service composition. Customized media delivery can be achieved through dynamic compositions of Service Specific Overlay Networks (SSONs). However, the presence of SSONs in dynamic environments raises the possibility of unexpected failures and quality degradations. Thus constructing, managing, and repairing corrupted service paths are challenging dilemmas. This thesis investigates the problem of autonomous SSON construction and management and identifies the drawbacks of current approaches. A novel multi-layered, autonomous, self-adaptive framework for constructing SSONs is presented. The framework includes a Hybrid Service Overlay Network layer (H-SON). The H-SON is a dynamic hybrid overlay dedicated to service composition for multimedia delivery in dynamic networks. Node placement in the overlay depends on the node’s stability, types and quality of provided services. Changes in stability and QoS of service nodes are reflected by dynamic re-organizations of the overlay. The H-SON permits fast and efficient searches for component services that meet client functional and quality expectations. Self-managed overlay nodes coordinate their behaviors to formulate a service composition path that meets the client’s requirements. Two approaches are presented in this work. The first illustrates how SSONs are established through dynamically adaptable MS-designed plans. The imprecise nature of nonfunctional service characteristics, such as QoS, is modeled using a fuzzy logic system. Moreover, semantic similarity evaluations enable us to include, in compositions, those services whose operations match, semantically, the requirements of the composition plan. Plan-based composition solutions restrict service discovery to defined abstract models. Our second composition approach introduces a semantic similarity and nearness SSON composition method. The objective is to free service nodes from the adherence to restrictive composition plans. The presented work illustrates a service composition solution that semantically advances service composition paths towards meeting users’ needs with each service hop while simultaneously guaranteeing user-acceptable QoS levels. Simulation results showcase the effectiveness of the presented work. Gathered results validate the success of our service composition methods while meeting user requirements.

The Service-Oriented Architecture (SOA) has become one of the most popular approaches to building large-scale network applications. The web service technologies are de facto the default implementation for SOA. Simple Object Access Protocol (SOAP) is the key and fundamental technology of web services. Service composition is a way to deliver complex services based on existing partner services. Service orchestration with the support of Web Services Business Process Execution Language (WSBPEL) is the dominant approach of web service composition. WSBPEL-based service orchestration inherited the issue of interoperability from SOAP, and it was furthermore challenged for performance, scalability, reliability and modifiability. I present an architectural approach for service composition in this thesis to address these challenges. An architectural solution is so generic that it can be applied to a large spectrum of problems. I name the architectural style RESTful Service Composition (RSC), because many of its elements and constraints are derived from Representational State Transfer (REST). REST is an architectural style developed to describe the architectural style of the Web. The Web has demonstrated outstanding interoperability, performance, scalability, reliability and modifiability. RSC is designed for service composition on the Internet. The RSC style is composed on specific element types, including RESTful service composition client, RESTful partner proxy, composite resource, resource client, functional computation and relaying service. A service composition is partitioned into stages; each stage is represented as a computation that has a uniform identifier and a set of uniform access methods; and the transitions between stages are driven by computational batons. RSC is supplemented by a programming model that emphasizes on-demand function, map-reduce and continuation passing. An RSC-style composition does not depend on either a central conductor service or a common choreography specification, which makes it different from service orchestration or service choreography. Four scenarios are used to evaluate the performance, scalability, reliability and modifiability improvement of the RSC approach compared to orchestration. An RSC-style solution and an orchestration solution are compared side by side in every scenario. The first scenario evaluates the performance improvement of the X-Ray Diffraction (XRD) application in ScienceStudio; the second scenario evaluates the scalability improvement of the Process Variable (PV) snapshot application; the third scenario evaluates the reliability improvement of a notification application by simulation; and the fourth scenario evaluates the modifiability improvement of the XRD application in order to fulfil emerging requirements. The results show that the RSC approach outperforms the orchestration approach in every aspect.

In recent years, Web services had been widely used on the Internet. Thanks to the convenient communication technologies and their inexpensive cost, communications between organizations is much easier, and Web services have become a de-facto standard for organizations to provide information and services. There are two different perspectives to describe Web service composition: orchestration and choreography. Works that verify a choreography model so as to alleviating some correctness problem such as deadlock have also been proposed. However the verification of implementations based on a choreography model has not be addressed. In this thesis, we propose an approach to verify the conformance of a set of Web services to a given choreography model and prune some candidate Web services which do not comply with the choreography model to avoid discordance with the choreography model and run-time errors. The proposed approach is evaluated by simulating 10,000 execution sequences of composite Web services. The experimental results show that our proposed method improves the performance of success rate and space usage by pruning the unsuitable candidate Web services.

Web services can be broadly classified into two types, namely effect providing (EP) services and data providing (DP) services. In this work, we address DP service composition problem that intends to satisfy user preference specified at the instance level, namely the expected occurrence. We first use the query rewriting method to identify a composition of service types that satisfies user¡¦s requirement and employ Bayesian Network model to express the causal relationship between exchange variables of DP service types. Service selection is then conducted by computing the posterior probability in the Bayesian Network. We conduct experiments to show that our proposed Bayesian Network-based method outperforms the other baseline methods in terms of execution success rate and data quality. It also has reasonable execution time.