Nowadays, Web Services technology has become a standard to integrate business processes across organizations. In general, there are two approaches for web service composition: Orchestration and Choreography. Orchestration is used to develop a single process that integrates services within or across an organization to achieve a business goal. On the other hand, Choreography is often used for cross-organizational communication and serves as a specification for communication. In a choreographed environment, each Web service is an independent entity, and each service selects the partner services using its own selection policy without knowing all the other services in the choreography. In this thesis, we use £k-calculus for modeling the Web Services. Afterwards, we propose an approach for each constituent process to choose and invoke other processes using the limited information provided by its partners. In our method, each service proclaims the requirments of its potential service providers (or consumers) and itself and provides to its partners. Subsequently each service will generate a local view using the information provided by its service consumers and providers to guide the selection. We evaluate our method by simulating 100,000 executions with different degrees of service availability. The experimental results indicate that our proposed method can indeed improve the success rate of the entire choreography.

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Service composition has risen from the need to make information systems more flexible and open. The Service Oriented Architecture has become the reference architecture model for applications carried by the impetus of Internet (Web). In fact, information systems are able to expose interfaces through the Web which has increased the number of available Web services. On the other hand, with the emergence of the Web 2.0, service composition has evolved toward web users with limited technical skills. Those end-users, named Y generation, are participating, creating, sharing and commenting content through the Web. This evolution in service composition is translated by the reference paradigm of Mashup and Mashup editors such as Yahoo Pipes! This paradigm has established the service composition within end users community enabling them to meet their own needs, for instance by creating applications that do not exist. Additionally, Web 2.0 has brought also its social dimension, allowing users to interact, either directly through the online social networks or indirectly by sharing, modifying content, or adding metadata. In this context, this thesis aims to support the evolving concept of service composition through meaningful contributions. The main contribution of this thesis is indeed the introduction of the social dimension within the process of building a composite service through end users' dedicated environments. In fact, this concept of social dimension considers the activity of compositing services (creating a Mashup) as a social activity. This activity reveals social links between users based on their similarity in selecting and combining services. These links could be an interesting dissemination means of expertise, accumulated by users when compositing services. In other terms, based on frequent composition patterns, and similarity between users, when a user is editing a Mashup, dynamic recommendations are proposed. These recommendations aim to complete the initial part of Mashup already introduced by the user. This concept has been explored through (i) a step-by-step Mashup completion by recommending a single service at each step, and (ii) a full Mashup completion approaches by recommending the whole sequence of services that could complete the Mashup. Beyond pushing a vision for integrating the social dimension in the service composition process, this thesis has addressed a particular constraint for this recommendation system which conditions the interactive systems requirements in terms of response time. In this regard, we have developed robust algorithms adapted to the specificities of our problem. Whereas a composite service is considered as a sequence of basic service, finding similarities between users comes first to find frequent patterns (subsequences) and then represent them in an advantageous data structure for the recommendation algorithm. The proposed algorithm FESMA, provide exactly those requirements based on the FSTREE structure with interesting results compared to the prior art. Finally, to implement the proposed algorithms and methods, we have developed a Mashup creation framework, called Social Composer (SoCo). This framework, dedicated to end users, firstly implements abstraction and usability requirements through a workflow-based graphic environment. As well, it implements all the mechanisms needed to deploy composed service starting from an abstract description entered by the user. More importantly, SoCo has been augmented by including the dynamic recommendation functionality, demonstrating by the way the feasibility of this concept.

Different types of web resources, such as Web Services, HTTP-based APIs and websites, can be located on the web to provide various services, such as information access and online banking. Such services are the basic building blocks to compose more complex functionality that cannot be achieved by a single service. Many service-oriented applications can be composed to fulfill similar functional requirements. Among various applications, a set of services can be frequently used together to deliver a unique functionality. Such set of services are called a service composition pattern. More specifically, a service composition pattern consists of a set of services and the control flow among the services. The reuse of the service composition patterns can facilitate the composition of new applications, improve existing applications and optimize maintenance process of services. To facilitate the identification and reuse of service composition patterns, we propose an approach that mines the service composition patterns from execution logs produced by service-oriented applications during runtime. Since the execution logs can be produced by heterogeneous web resources, we propose a unified description schema to describe various web resources in order to identify functionally similar services of different types. This helps reveal complete service composition patterns. Then we identify frequently associated services using Apriori algorithm and heuristics. Finally, we recover the control flow among the services using the event graph and process mining techniques. The effectiveness of the approach is evaluated through two case studies. The result shows that the unified description schema facilitates the identification of similar services of different types and our approach can effectively identify service composition patterns. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-09-29 18:08:07.55

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.

During the past decade service-orientation has become a popular design paradigm, offering an approach in which services are the functional building blocks. Services are self-contained units of composition, built to be invoked, composed, and destroyed on (user) demand. Service-oriented systems (SOS) are a collection of services that are developed based on several design principles such as: (i) loose coupling between services (e.g., inter-service communication can involve either simple data passing or two or more connected services coordinating some activity) that allows services to be independent, yet highly interoperable when required; (ii) service abstraction, which emphasizes the need to hide as many implementation details as possible, yet still exposing functional and extra-functional capabilities that can be offered to service users; (iii) service reusability provided by the existing services in a rapid and flexible development process; (iv) service composability as one of the main assets of SOS that provide a design platform for services to be composed and decomposed, etc. One of the main concerns in such systems is ensuring service quality per se, but also guaranteeing the quality of newly composed services. To accomplish the above, we consider two system perspectives: the developer's and the user's view, respectively. In the former, one can be assumed to have access to the internal service representation: functionality, enabled actions, resource usage, and interactions with other services. In the second, one has information primarily on the service interface and exposed capabilities (attributes/features). Means of checking that services and service compositions meet the expected requirements, the so-called correctness issue, can enable optimization and possibility to guarantee a satisfactory level of a service composition quality. In order to accomplish exhaustive correctness checks of design-time SOS, we employ model-checking as the main formal verification technique, which eventually provides necessary information about quality-of-service (QoS), already at early stages of system development. ~As opposed to the traditional approach of software system construction, in SOS the same service may be offered at various prices, QoS, and other conditions, depending on the user needs. In such a setting, the interaction between involved parties requires the negotiation of what is possible at request time, aiming at meeting needs on demand. The service negotiation process often proceeds with timing, price, and resource constraints, under which users and providers exchange information on their respective goals, until reaching a consensus. Hence, a mathematically driven technique to analyze a priori various ways to achieve such goals is beneficial for understanding what and how can particular goals be achieved. This thesis presents the research that we have been carrying out over the past few years, which resulted in developing methods and tools for the specification, modeling, and formal analysis of services and service compositions in SOS. The contributions of the thesis consist of: (i)constructs for the formal description of services and service compositions using the resource-aware timed behavioral language called REMES; (ii) deductive and algorithmic approaches for checking correctness of services and service compositions;(iii) a model of service negotiation that includes different negotiation strategies, formally analyzed against timing and resource constraints; (iv) a tool-chain (REMES SOS IDE) that provides an editor and verification support (by integration with the UPPAAL model-checker) to REMES-based service-oriented designs;(v) a relevant case-study by which we exercise the applicability of our framework.The presented work has also been applied on other smaller examples presented in the published papers. / Under det senaste årtiondet har ett tjänstorienterat paradigm blivit allt-mer populärt i utvecklingen av datorsystem. I detta paradigm utgör så kallade tjänster den minsta funktionella systemenheten. Dessa tjänster är konstruerade så att de kan skapas, användas, sammansättas och avslutas separat. De ska vara oberoende av varandra samtidigt som de ska kunna fungera effektivt tillsammans och i samarbete med andra system när så behövs. Vidare ska tjänsterna dölja sina interna implementa-tionsdetaljer i så stor grad som möjligt, samtidigt som deras fulla funktionalitet ska exponeras för systemdesignern. Tjänsterna ska också på ett enkelt sätt kunna återanvändas och sammansättas i en snabb och flexibel utvecklingsprocess.En av de viktigaste aspekterna i tjänsteorienterade datorsystem är att kunna säkerställa systemens kvalitet. För att åstadkomma detta ärdet viktigt att få en djupare insikt om tjänstens interna funktionalitet, i termer av möjliga operationer, resursinformation, samt tänkbar inter-aktion med andra tjänster. Detta är speciellt viktigt när utvecklaren har möjlighet att välja mellan två funktionellt likvärda tjänster somär olika med avseende på andra egenskaper, såsom responstid eller andra resurskrav. I detta sammanhang kan en matematisk beskrivning av en tjänsts beteende ge ökad förståelse av tjänstemodellen, samt hjälpa användaren att koppla ihop tjänster på ett korrekt sätt. En matematisk beskrivning öppnar också upp för ett sätt att matematiskt resonera kring tjänster. Metoder för att kontrollera att komponerade tjänstermöter ställda resurskrav möjliggör också resursoptimering av tjänster samt verifiering av ställda kvalitetskrav.I denna avhandling presenteras forskning som har bedrivits under de senaste åren. Forskningen har resulterat i metoder och verktyg föratt specificera, modellera och formellt analysera tjänster och sammansättning av tjänster. Arbetet i avhandlingen består av (i) en formell definition av tjänster och sammansättning av tjänster med hjälp avett resursmedvetet formellt specifikationsspråk kallat Remes; (ii) två metoder för att analysera tjänster och kontrollera korrektheten i sammansättning av tjänster, både deduktivt och algoritmiskt; (iii) en modell av förhandlingsprocessen vid sammansättning av tjänster som inkluderar olika förhandlingsstrategier; (iv) ett antal verktyg som stödjer dessa metoder. Metoderna har använts i ett antal fallstudier som är presenterade i de publicerade artiklarna. / Contesse

Web Services are self-contained, self-describing, modular applications that can be published, located, and invoked through XML artefacts across the Web. Web services technologies can be applied to many kinds of applications, where they offer considerable advantages compared to the old world of product-specific APIs, platform-specific coding, and other &ldquo / brittle&rdquo / technology restrictions. Currently there are millions of web services available on the web due to the increase in e-commerce business volume. Web services can be discovered using public registries and invoked through respective interfaces. However how to automatically find, compose, invoke and monitor the web services is still an issue. The automatic discovery, composition, invocation and monitoring of web services require that semantics will be attached to service definitions. The focus of this thesis is on the composition of web services. The approach taken is to extend the DAML-S ontology that is used to define the semantics of services to include the &ldquo / succeeding services&rdquo / for any service provided. These definitions for individual service instances are declared by the service providers. They are presented to the users of the service to construct a workflow in a mobile environment. The workflow generated is represented both graphically in the mobile device and in XML-format as a BPEL4WS document. The aim of this thesis is to prove that it is possible to build a semi-automatic web service composition utility incorporating semantic constructs, using a mobile device. The generated workflow is suitable for deployment on an engine where it can be executed multiple times with different configurations.

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.

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.

Web services have become a prominent paradigm for building of both inter and intra-enterprise business processes. These processes are composed from existing Web services based on defined requirements. Standards and techniques have been developed to aid in the dynamic composition of services. However, these approaches are limited when it comes to the handling of unexpected events. This dissertation presents the results of experiments that investigated numerous problems related to Web service composition processes. Based on the investigation, a fault taxonomy was formulated. Faults were grouped into three broad categories, each representing a distinct problem stage. The investigation into faults gave rise to the issue of fault recovery and continued process execution. A list of requirements for self-healing Web service composition was identified, while a new self-healing cycle was exploited based on the MAPE cycle (Monitor, Analyzer, Planner, Executive). The proposed self-healing composition cycle consists of three modules: Plan Generation Module, Plan Execution Module and Failure Analysis Module. The plan execution module, consisting of the execution and run-time monitoring phases, and the failure analysis module, consisting of the analysis and sensemaking phases, were found to be vital to self-healing Web service composition. Self healing Web service composition and the goal of self-healing were achieved through the use of Hierarchical Task Network (HTN) planning systems. / Dissertation (MSc)--University of Pretoria, 2009. / Computer Science / unrestricted