Automated Web Service Composition and Execution Based on Semantic Web Technology

網路服務技術在分散式資訊系統架構下為服務提供的方式和趨勢，並可根據使用者複雜的需求，將多個網路服務組合成一個新的網路服務。以現有的網路服務技術，實現自動化找尋所需求的服務、自動化組合服務，為一很大的困難與挑戰，目前有許多語意網技術結合網路服務實現自動化找尋網路服務、自動化服務組合、自動化服務執行的計畫和研究正在進行當中。 在本論文中，我們的目的為二：以語意網技術應用在網路服務技術上，實作一個客製化系統；動態組合現有網路服務，滿足使用者的需求。我們使用現有的語意網與網路服務技術：WSDL、SWRL、OWL、BPEL4WS。描述網路服務的語意資訊，我們使用WSDL定義服務介面的描述，及以OWL定義服務特徵的描述。根據使用者服務的需求描述，以及以OWL語意化的網路服務所定義的Service Profile，透過自動推理工具進行服務描述比對，找到滿足使用者需求的服務。 我們整理出一個處理不同需求的條件限制(Constraint)的方法，藉由邏輯描述與推理引擎和規則與相關規則引擎，以確保條件限制的一致性(Consistency)；SWRL用來補足OWL-DL語意的不足，透過role composition，使用自動推理工具推論出新的關係與知識。我們也提出一個網路服務執行的架構，依據BPEL4WS的生命週期，提供自動化網路服務執行的實作參考。 根據服務組合架構(Service Composition Architecture)，應用以上技術，我們以旅遊業為例，開發一個客製化雛型系統組合旅遊相關服務。我們相信，本論文在解釋網路服務自動化組合與執行為一個很實用的參考，也為語意網技術應用在網路服務上提供一個很完整的應用系統。Web services provide an implementation architecture for a distributed information system. As Web services emerge and expand, they can be used and be re-composed as a new Web service to complete complicated tasks. Discovering expected services and composing different services are great challenges. However, with Semantic Web technologies, Web services can be located precisely according to users’requirements and can be composed to handle the problem of composition. There are many ongoing studies and research projects on applications of Semantic Web technologies to Web services that provide automatic service discovery, service composition, and service execution. In this thesis, our objective is twofold: (1) implement a customized system that applies Semantic Web technologies to Web services and (2) dynamically synthesize existing services on the World Wide Web in order to fulfill the user's needs. The architecture of the application system is built on an ontology that is defined by Web Ontology Language (OWL) for a specific domain. Service interfaces containing the necessary information for invoking a service are described by Web Service Description Language (WSDL). Since the user's requirements are often ambiguous, automatic service matching with subsumption reasoning based on Description Logics (DLs) is a basic task. We also use Semantic Web Rule Language (SWRL) to increase the expressive power of concepts when describing complicated relationships between concepts. The composition of Web services is the most important aspect in Semantic Web services. We consider service composition in terms of logic theory and collate several composition patterns encountered in the real world. After composition, the services can be invoked and executed in the subsequent task. The execution process flows in terms of the execution order and interaction between Web services are defined by Business Process Execution Language for Web Service (BPEL4WS). Moreover, we propose a service execution module that provides a prototype of implementing service execution. We extend the execution fuction to a prototype system “the Traveller” that aims to help users discover, combine, and invoke the desired Web services for the tourism domain. We believe this thesis will be useful for explaining the automatic composition and execution of Web services, as well as providing examples of application of Semantic Web technologies.1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Related Work 6 2.1 Semantic Web Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1 Web Service Modeling Ontology(WSMO) . . . . . . . . . . . . . . 6 2.1.2 OWL-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 Modeling Ontology of Time and Value . . . . . . . . . . . . . . . . . . . 10 2.3 Web Service Composition . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 SATINE Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.5 European Semantic Systems Initiative (ESSI) . . . . . . . . . . . . . . . 13 3 Preliminaries 15 3.1 Description Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.1.1 Description Logics Syntax and Semantics . . . . . . . . . . . . . . 17 3.2 OWL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.3 Web Service Description Language(WSDL) . . . . . . . . . . . . . . . . . 20 3.4 Semantic Web Rule Language(SWRL) . . . . . . . . . . . . . . . . . . . 21 3.5 Web Service Business Process Execution Language(WS-BPEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4 Service Composition and Execution Based on Semantic Technology 26 4.1 Overview of Web Service Composition Architecture Based on Semantic Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.1.1 Web Service Composition . . . . . . . . . . . . . . . . . . . . . . 27 4.1.2 Design of Web Service Composition Architecture Based on Semantic Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.1.3 Service Profile and Service Interface . . . . . . . . . . . . . . . . . 33 4.2 Semantic Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2.1 Ontology Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2.2 Service Composition Mechanism . . . . . . . . . . . . . . . . . . . 39 4.2.3 Service Execution Based on Semantic Technology . . . . . . . . . 41 4.3 Constraint Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.3.1 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.3.2 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.3.3 Value Partition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.4 Service Composer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4.4.1 Design of the Service Composer . . . . . . . . . . . . . . . . . . . 46 4.4.2 Architecture of the Service Composer . . . . . . . . . . . . . . . . 48 4.5 Service Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.5.1 Design of the Service Execution Module . . . . . . . . . . . . . . 52 4.5.2 Architecture of the Service Execution Module . . . . . . . . . . . 52 4.5.3 Development of the Business Process Execution Language . . . . 54 5 Implementation - The Traveller 58 5.1 The System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 5.2 Service Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 5.2.1 Trip Requirement Description . . . . . . . . . . . . . . . . . . . . 60 5.2.2 Service Advertisement Description . . . . . . . . . . . . . . . . . 62 5.3 Implementation of the Prototype System . . . . . . . . . . . . . . . . . . 62 5.3.1 Implementation of the Service Composer . . . . . . . . . . . . . . 63 5.4 Ontology Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.4.1 The Tourism Domain Ontologies . . . . . . . . . . . . . . . . . . 67 5.4.2 The Requirement Ontology . . . . . . . . . . . . . . . . . . . . . 70 5.4.3 The Advertisement Ontology . . . . . . . . . . . . . . . . . . . . 72 5.5 Constraint Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.5.1 Time Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.5.2 Budget Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.6 Constraint Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.6.1 PAL Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.6.2 SWRL Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5.7 System Integrated User Interface . . . . . . . . . . . . . . . . . . . . . . 84 6 Conclusion 86 6.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8