|dc.description.abstract||Service-Oriented Architecture (SOA) has emerged as a promising paradigm for building loosely coupled, standard-based and Web-enabled distributed applications and systems. The essential notion and technology of SOA is Web service which is the high level of abstraction of functionality with well-defined interfaces. If a Web service is further equipped with well-defined semantics, it is termed Semantic Web service. With the power of Semantics of Web services, SOA has created many new opportunities to meet the challenge of enterprise integration and provides great potentials for automated integration. However, this promising paradigm has also imposed a great challenge to the service discovery, invocation, composition, self-healing capability and so on. Among all those issues, service composition, which is defined as aggregation of other services to provide a more sophisticated, value-added service, is at the core of many applications of Web services. From a service oriented perspective, application integration which is a long standing issue in industry can be achieved via service composition. Nevertheless, the dynamics in real application context when addressing the service composition very much complicate the matter, and it is often desirable to accomplish composition with high degree of serviceability, especially when environment changes or when services previously used becomes unavailable. One of approaches to serviceability is the capability of self-healing with less or no external interventions when changes occur. Service composition and self healing of composite services are the major concerns of the research work described in this thesis. The main objectives are to extensively explore semantics for facilitating Web service composition and for realizing dynamic self-healing for composite services in a semantic-enhanced service-oriented manufacturing Collaborative Virtual Enterprise (CVE).
A CVE is a temporary alliance of enterprises to share skills or core competencies and resources in order to better respond to business opportunities in a more collaborative rather than competitive manner. Dynamism is a salient feature of CVE. A CVE needs to be dynamically formulated, its business processes need to be dynamically configured and executed to respond to the dynamic market. A CVE needs to quickly integrate its systems, applications, and services to fulfill its business goals. Taking semantic Web service-oriented approach, we shall first establish a semantic rich service-oriented manufacturing CVE where a collection of Semantic Web services are developed.
Within the service-oriented paradigm, two different approaches – BPEL and OWL-S are investigated to realize service composition in a service-oriented manufacturing CVE. The critical analysis of BPEL and OWL-S is conducted in the manufacturing CVE scenario. Five key criteria for evaluating technologies of service composition are identified. Moreover, semantic-driven services composer based on OWL-S is developed and the goal-oriented forward-chaining algorithm is presented.
In order to systematically address semantic web service composition, a business rule enhanced semantic service composition framework is further presented and analyzed. We adopt the divide-and-conquer strategy and propose a hierarchical composition architecture to handle tasks of complex service composition. In this framework, the description of each Web Service is enhanced with rule-based modeling of the essential business logic behind the service interface. A formal notion of service utilities has been provided. Complete processes for calculating the service utilities have also been introduced through processing and evaluating these business rules. A PC manufacturing CVE derived from a practical industrial setting is designed and a prototype system is developed to experimentally evaluate the effectiveness of our service composition framework.
In a practical industrial setting, the effective and efficient service composition is often not sufficient for dynamic natures of CVE. Once formulated, a composite service for a business goal must be able to address many dynamic changing issues, and in this case self-healing capability of a composite service has appeared as an attractive approach. Self-healing refers to a capability of a service to maintain its serviceability by healing itself when its component service becomes unavailable or downgraded. In this research, a self-healing capable composite service execution system is proposed. The execution system takes advantage of the complementary strengths of OWL-S and BPEL in the following ways: (1) a dynamic self-healing mechanism is proposed which can dynamically identify suitable alternatives and replace faulty services such that a composite service can be performed successfully despite of unexpected exceptions; (2) an OWL-S process to BPEL process Mapper is presented which can translate OWL-S process to BPEL process and meanwhile embed the self-healing mechanism into BPEL workflow. Semantic Web service technology plays its part for service matching and selection during the self-healing process in a sense that Semantic Web services are equipped with rich business rules in a domain-dependent manner. A concrete scenario – PC manufacturing CVE is used to demonstrate the effectiveness of self-healing capable composite service execution system.||