Mobile devices have evolved over the years from resource constrained devices that supported only the most basic tasks to powerful handheld computing devices. However, the most significant step in the evolution of mobile devices was the introduction of wireless connectivity which enabled them to host applications that require internet connectivity such as email, web browsers and maybe most importantly smart/rich clients. Being able to host smart clients allows the users of mobile devices to seamlessly access the Information Technology (IT) resources of their organizations. <p>One increasingly popular way of enabling access to IT resources is by using Web Services (WS). This trend has been aided by the rapid availability of WS packages/tools, most notably the efforts of the Apache group and Integrated Development Environment (IDE) vendors. But the widespread use of WS raises questions for users of mobile devices such as laptops or PDAs; how and if they can participate in WS. Unlike their wired counterparts (desktop computers and servers) they rely on a wireless network that is characterized by low bandwidth and unreliable connectivity.<p>The aim of this thesis is to enable mobile devices to host Web Services consumers. It introduces a Model-Driven Dual Caching (MDDC) approach to overcome problems arising from temporarily loss of connectivity and fluctuations in bandwidth.

In the Service Oriented Architecture (SOA) services are computational elements that are published, discovered, consumed and aggregated across platform and organizational borders. The most commonly used technology to achieve SOA are Web Services (WSs). This is due to standardization process (WSDL, SOAP, UDDI standards) and a wide range of available infrastructure and tools. A very interesting aspect of WSs is their composeability. WSs can be easily aggregated into complex workflows, called Composite Web Services (CWSs). These compositions of services enable further reuse and in this way new, even more complex, systems are built.<p>Although there are many languages to specify or implement workflows, in the service-oriented systems BPEL (Business Process Execution Language) is widely accepted. With this language WSs are orchestrated and then executed with specialized engines (like ActiveBPEL). While being very popular, BPEL has certain limitations in monitoring and optimizing executions of CWSs. It is very hard with this language to adapt CWSs to changes in the performance of used WSs, and also to select the optimal way to execute a CWS. <p>To overcome the limitations of BPEL, I present a model-aware approach to execute CWSs. To achieve the model awareness the Coloured Petri Nets (CPN) formalism is considered as the basis of the execution of CWSs. This is different than other works in using formal methods in CWSs, which are restricted to purposes like verification or checking of correctness. Here the formal and unambiguous notation of the CPN is used to model, analyze, execute and monitor CWSs. Furthermore this approach to execute CWSs, which is based on the CPN formalism, is implemented in the model-aware middleware. It is also demonstrated how the middleware improves the performance and reliability of CWSs.

The use of service-oriented (SO) distributed systems is increasing. Within service orientation web services (WS) are the de facto standard for implementing service-oriented systems. The consumers of WS want to get uninterrupted and reliable service from the service providers. But WS providers cannot always provide services in the expected level due to faults and failures in the system. As a result the fault management of these systems is becoming crucial. This work presents a distributed event-driven architecture for fault management of Web Services. According to the architecture the managed WS report different events to the event databases. From event databases these events are sent to the event processors. The event processors are distributed over the network. They process the events, detect fault scenarios in the event stream and manage faults in the WS.

This research explores the problems associated with caching of SOAP Web Service request/response pairs, and presents a domain independent framework enabling transparent caching of Web Service requests for mobile clients. The framework intercepts method calls intended for the web service and proceeds by buffering and caching of the outgoing method call and the inbound responses. This enables a mobile application to seamlessly use Web Services by masking fluctuations in network conditions. This framework addresses two main issues, firstly how to enrich the WS standards to enable caching and secondly how to maintain consistency for state dependent Web Service request/response pairs.

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.

Service-Oriented Architecture (SOA) is intended for the integration of heterogeneous applications. Complex business processes are composed by a group of specific Web services using WS-BPEL (Business Process Execution Language), and these Web services may be designed by the enterprise itself or third-party services providers. Today there are many WS-BPEL engines that support the deployment and execution of WS-BPEL files. However, the WS-BPEL activities have to be pre-defined, and if at runtime a Web service call fails, the entire business process is pronounced to be failed, thereby jeopardizing the reliability of SOA. Although the WS- BPEL supports compensation mechanism, it is complex and not flexible. In this work, we propose a process design model to support dynamic Web services selection that eases the designer¡¦s job. This model has been implemented, and the prototype is evaluated to demonstrate that it indeed improves the overall business process reliability.

Emergency response is a time critical work that needs team work from different organizations with various specialties. It also needs to integrate existing information system to collect and assemble necessary knowledge and resources for critical emerging tasks and use it to plan for collaborative problem solving In this study, we propose the methodology to automate the traditional emergency patient transfer process by connecting different organization¡¦s information systems through Web services with BPEL4WS. Via Web services, the medical resources information can be requested according to patient conditions, and resource reservation decision can be made online. Via BPEL4WS, heterogeneous information systems in different organizations can be connected and executed automatically in any predefined process without limit human intervention. The willingness of hospitals to share various levels of resource availability information to Emergency Operation Center (EOC) to coordinate regional medical resource distribution is critical to make Web service platform work. Therefore, this study examines the correlation of individual hospitals¡¦ performance in terms of resource utilization with hospital¡¦s information sharing with EOC. We investigate the effects from sharing information to EOC which adopts three policies of releasing hospital status information through simulation under different conditions in emergency occurrence and occupied hospital resources. Our findings from the simulations imply that the best policy for EOC to adopt in order to make Web services workable in handling medical emergency is to accord different conditions to adopt different suitable policies. For hospitals, if they want to get the maximum resources utilization, it had better to refer to different condition to adopt different information sharing strategies.

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.

In our daily lives, people constantly need to schedule their activities to meet their personal goals. Many of these activities involve the interaction with organization sectors, which must follow certain regulations in terms of input data, doable time and places. These regulations form personal processes. In previous work, [Chen01] proposed a personal process model that define a personal process as a set of tasks and a coordination on the tasks and a personal workflow system architecture. However, the proposed system is solely to facilitate a mobile user in deciding when, where, and how to process a task. We have noticed that many processes initiated by an individual often involve business processes coming from different organizations. Our objective in this thesis is to revise the personal process model proposed in [Chen01] by incorporating business processes existing in different sectors, developing a simpler query method, and extending personal workflow architecture in support of the new model. In our architecture, the management of personal processes involves three parties: the service provider, the template provider and the PWFMS. The service providers supply personal processes, each of which enable users to achieve a specific goal, and keep track of the status of executed tasks. The template providers incorporate several personal processes from different service providers and form a useful template for a user. The PWFMSs assist users in managing personal processes. In order to prove our idea, we implemented a prototype of the architecture.

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.