Apply Page rank-like approach to web service workflow field. At the same time, no one try to device an engine that validates a composite web service workflow by means of FSM, which has formal theoretical base. In this work, we presented an algorithm to build up the composition FSM, which is a criterion to know a composition is feasible or not. We introduce nested cycle hierarchy to address the problem that PageRank weight assignment would favor cycle structure.

Nowadays, web services have been widely utilized on the Internet. The communication of organizations becomes much easier; thanks to the advances of computer and communication technologies and the inexpensive cost, and the integration of applications within and across business organizations is a trend. In general, there are two approaches in composing web services inside or outside an organization: orchestration and choreography. Previous work in the web service selection is usually based on orchestration model and focuses on the interest of a single party. However, in many application scenarios, business goals are achieved by pair-wise interactions among a set of WSs, and there is no single entity that is in charge of selecting web service for each task. Each web service can autonomously perform web service selection. By autonomy, we maintain that each WS is aware of only its partner web services. In such a choreographic environment, we study the kind of information that each web service should provide to its partner web services and how each web service should perform web service selection so as to maximize the chance of successfully accomplish a business goal. The proposed approach is evaluated by simulating 10,000 execution sequences of the target WS and assumed a fixed operation reliability for each delegation. The experimental results show that our proposed method is close to centralized method and better than other two selection methods, namely random and view-based-propagation-free.

Open distributed environments such as the World Wide Web facilitate information sharing but provide limited support to the protection of sensitive information and resources. Web services have become a part of components for quickly building a business process that satisfies the business goal of an organization, and access control is imperative to prevent the illegal access of sensitive information. In recent years, several researches have investigated the Web services-based workflow access control problem, and selection approaches for choosing the performer for each task so as to satisfy all access control constraints have been proposed. Based on the role-based access control model, we focus on two types of access control: separation of duties and binding of duties. Both role-level and participant-level of SoDs and of BoDs that need to be dynamically enforced are considered in this thesis. While dealing with complex and flexible business logics, we use rule engine to reasons with the business facts to get the result based on business rules. The proposed approach is evaluated by a workflow scenario and is shown to be flexible to develop new process with dynamic access control constraints at the cost of higher execution time.

As the emergence of SOA concept, web services has became a key technology to achieve the seamless system interoperability and collaborations with enterprises partners. Since many available web services provide overlapping or identical functionality, when it comes to composing a composite web service, a choice needs to be made for selecting an appropriate component web service. Dynamic web service selection refers to determining a subset of component web services to be invoked so as to orchestrate a composite web service. Previous work in web service selection usually assumes the invocations of web service operations to be independent of on another. But this assumption however does not hold in practice as both the composite and component web services often impose some orderings on the invocation of their operations to represent its business logic. Such orderings constrain the selection of component web services to orchestrate the composite web service. We therefore propose to use finite state machine (FSM) to model the invocation order of web service operations. We define a measure, called aggregated reliability, to measure the probability that a given state in the composite web service will lead to successful execution in the context where each component web service may fail with some probability. We show that the computation of aggregated reliability is equivalent to eigenvector computation. We also propose two strategies to select component web services that are likely to successfully complete the execution of a given sequence of operations. For our approach to work in a practical environment, the dominating composition language BPEL for specifying the operation invocation orders will be transformed into an abstract FSM. We also proposed a prototype for realizing our dynamic WS selection. Our experiments on a generated set of web service operation sequences show that our proposed strategies perform better than two baseline selection strategies.

Web services have emerged as a de facto standard for encapsulating services within or across organization boundaries. Various proposals have been made to compose Web services into workflow so as to meet the goal previously unaccomplished by a single entity. This thesis intends to investigate the Web services-based workflow access control problem. It starts by analyzing the various access control constraints proposed in the literatures and presenting three primitive constructs that are capable of specify these constraints. It then proposes a Web service selection approach that dynamically chooses a performer for each task in the workflow, not only to satisfy all access control constraints currently but also to increase the chance of completing the entire process in the future. The proposed approach is evaluated using synthetic data and is shown to result in the execution that is less likely to violate any specified access control constraints.

Web services have become the de facto standards as components for quickly building a business process that satisfies the business goal of an organization. Nowadays, Web services have found its way into describing the functions of automatic tasks as well as manual tasks. An important part in the specification of a business process, especially for manual tasks, is the access control. This thesis considers both types of tasks involved in a Web services-based process with its corresponding access control problem and proposes a selection approach for choosing the performer for each task so as to satisfy all access control constraints. Based on the role-based access control model, we focus on two types of access control: separation of duties (SoD) and binding of duties (BoD). Both role-level and participant-level of SoDs and of BoDs that need to be dynamically enforced and these constraints are considered in this thesis. The proposed performer selection approach is evaluated by a workflow scenario and is shown to have the highest chance of satisfying all predefined access control constraints when compared to other methods.

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.

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.

Un service Web est un moyen d'offrir des fonctionnalités sur un réseau en utilisant des normes ouvertes pour la description et l'invocation. Les services Web représentent une réalisation importante de l'Architecture Orientée Service (AOS), à l'aide de qui, les applications peuvent être développées rapidement avec un coût bas par couplage faible les services sur un réseau. Cela nécessite la découverte et la composition des ensembles de services interopérables, selon certaines exigences fonctionnelles et non fonctionnelles. Les services Web confrontent de nombreux défis quant à leur découverte et sélection, en raison de plusieurs facteurs tels que: le nombre important de services, le manque de registres publics capables d'offrir des mécanismes efficaces de récupération de service, de leur nature dynamique qui impose divers aspects de QoS tels que la disponibilité, le temps de réponse, etc, et le manque de sémantique dans leurs descriptions d'interface. Dans cette thèse, nous avons deux objectifs principaux. Notre premier objectif est de faciliter la sélection des services Web et d'assurer la continuité du service dans des compositions de services Web. Par conséquent, nous proposons une approche basée sur l'analyse formelle de concepts (AFC) pour classer les services Web dans un premier temps par mots clés, puis par les valeurs de similarité entre leurs opérations. Cette classification est représentée comme un treillis de concepts qui révèle les relations entre les services, ce qui facilite la sélection d'un service nécessaire ainsi que l'identification des potentiels sauvegardes (substitutions en cas de panne). Notre deuxième objectif est de guider l'utilisateur en effectuant une sélection optimisée basée sur des plusieurs critères. Nous définissons un descripteur pour l'utilisateur qui spécifie des exigences fonctionnelles et non fonctionnelles. Dans ce descripteur, les propriétés fonctionnelles sont spécifiées comme un ensemble de mots-clés. Les propriétés non fonctionnelles représentent les niveaux attendus de QoS (bon, mauvais, moyen, ..) ainsi que la composition de services exprimée en tant que liens entre les propriétés fonctionnelles spécifiées. Afin d'atteindre cet objectif, nous proposons une approche basée sur l'analyse relationnelle de concepts (ARC) qui classifie les services Web en treillis de concepts similaires à la AFC, mais enrichis avec les propriétés non-fonctionnelles. Nous proposons également un mécanisme permettant d'interroger le concept de treillis résultant basée sur RCA, selon les exigences spécifiées dans le descripteur. Nous avons validé notre proposition en utilisant des services Web réels extraits de Service-Finder et Seekda (des moteurs de recherche de services Web). Pour l'approche basée sur la AFC, nous avons récupéré un total de 145 services Web que nous avons classés en fonction de leur fonctionnalité. Nous avons montré comment sélectionner efficacement un service offrant les fonctionnalités requises et la manière d'identifier ses sauvegardes. Pour l'approche basée sur RCA, nous avons récupéré 901 services Web que nous avons classés selon leur niveau de QoS et de composabilité. Nous avons vérifié que cette approche permet une sélection efficace des services correspondant aux exigences fonctionnelles et non fonctionnelles spécifiées. / A Web service is a way of offering functionality over a network using open standards for description and invocation. Web services represent an important realization of Service-Oriented Architectures (SOA), using which, applications can be developed rapidly with a low cost by loosely coupling services over a network. This necessitates discovering and composing sets of interoperable services, according to some functional and non-functional requirements.Web services face many challenges regarding their discovery and selection, due to several factors like: the fairly large number of services, the lack of public registries capable of offering efficient service retrieval mechanisms, their dynamic nature which imposes various QoS aspects such as availability, response time, etc., and the lack of semantics in their interface descriptions.In this thesis, we have two main objectives. Our first objective is to facilitate Web service selection and assure service continuity in Web service compositions. Therefore, we propose an approach based on Formal Concept Analysis (FCA) to classify Web services first by keywords then by similarity values between their operations. This classification is represented as a concept lattice that reveals the relations between the services, which facilitates the selection of a needed service as well as the identification of its potential backups (substitution in case of failure).Our second objective is to guide the user towards performing an optimized multi-criteria based selection. We define a user requirements descriptor that specifies the needed functional and non-functional properties. Inside this descriptor, functional properties are specified as a set of keywords. Non-functional properties represent the expected QoS levels (good, bad, medium, ..) as well as the composition of services expressed as links between the specified functional properties. In order to meet this objective, we propose an approach based on Relational Concept Analysis (RCA) that classifies Web services into concept lattices similar to FCA, but enriched with the non-functional properties. We also propose a mechanism to query the resulting RCA-based concept lattices, according to the requirements specified in the descriptor.We validated our proposition using real Web services retrieved from Service-Finder and Seekda Web service search engines. For the FCA-based approach, we retrieved a total of 145 Web services that we classified by their functionality. We showed how to select efficiently a service offering the required functionality and how to identify its backups.For the RCA-based approach, we retrieved 901 Web services that we classified by their QoS and composability levels. We verified that the approach allows an efficient selection of services corresponding to the specified functional and non-functional requirements.

Seleção de serviços em composições distribuídas considera principalmente a qualidade de serviço que atenda requisitos estabelecidos pelo usuário, como por exemplo, preço. No entanto, problemas relacionados a execução de composições de serviços podem ocorrer quando não se considera aspectos relacionados à rede e ao hardware, que afetam diretamente o desempenho da composição. Esse problema se agrava em composições coreografadas, pois a característica descentralizada requer um maior esforço para que essas informações possam ser consideradas em uma perspectiva global. Dessa forma, apesar da descentralização apresentar vantagens, é necessário que requisitos de qualidade de serviço da composição também sejam considerados em coreografias de serviços web para que a escolha de serviços para desempenhar um papel leve em consideração parâmetros importantes que podem afetar no desempenho da composição. Este trabalho apresenta um mecanismo, implementado sobre o framework OpenKnowledge, para selecionar serviços web em ambientes coreografados considerando primeiramente estimativas de atraso, taxa de perda e por fim considera a utilização de outros parâmetros, como utilização de CPU. Os primeiros experimentos em diferentes cenários de rede confirmaram as vantagens da proposta em relação a um seletor de serviços que ignora aspectos relacionados com a rede. Obteve-se ganhos de 20 a 97% no que diz respeito ao tempo total da execução da coreografia. Em seguida, experimentos inserindo utilização de CPU na escolha dos serviços confirmaram as vantagens de utilização de diferentes parâmetros para seleção de serviços em coreografias. / Selection of services in distributed compositions mainly considers the quality of service that meets requirements set by the user, such as price. However, problems related to the execution of service compositions may occur when aspects related to network and hardware, which directly affect the performance of the composition, are not taken in consideration. This problem is aggravated in choreographed compositions because the decentralized feature requires a greater effort so that this information may be considered in a global perspective. Thus, despite the decentralization advantages, it is necessary that the service quality requirements of the composition may also be considered in the choreography of web services so that the choice of services may play a role that takes into account important parameters, which can affect the performance of the composition. This dissertation presents a mechanism, implemented on the OpenKnowledge framework, to select web services in choreographed environments. First, considering delay estimates, loss rate and finally the use of other parameters, such as CPU utilization. The first experiments on different network scenarios confirmed the proposal advantages in relation to a selection mechanism that bypasses aspects of the network. It was obtained gains from 20% to 97% considering the total time of execution of the choreography. Then, experiments inserting CPU utilization in the choice of services confirmed the advantages of using different parameters for selection of services in choreography.