WS-BPEL經過標準程序的定義與組合後，可以將不同的網路服務組裝成一個具結構性的自動化企業流程。流程中所引用的網路服務必須在設計階段明確定義規格，流程執行時一旦出現非預期的網路服務調用失敗，將可能導致整個流程宣告失敗。過去廣泛地探討如何提出最佳化的動態網路服務組合，卻很少去提出如何在WS-BPEL執行環境下，實作動態網路服務綁定以滿足資料交換正確及服務品質的需求。
在過去相關的研究，大多採用透過代理人或是延伸系統架構方式來實作。除此之外，不同資料介面之間的資料交換方式也沒有被提出來討論。在我們的研究中，我們利用WS-BPEL 2.0提出的Extension Activity擴充規格並透過設計者所制訂之資料交換轉換規則及候選服務清單來實作動態及異質網路服務綁定。實驗結果顯示，我們所提出的方法確實能夠在可靠度及效能上都具有優越的表現。

Composing different Web services into a structured and complex automatic workflow is the core of Service-Oriented-Architecture, and the de-facto composition standard is WS-BPEL. However, most compositions using BPEL specify the constituent Web services at design time. Once the invocation of any Web service fails (due to network failure, server failure, or interface mismatch), the entire process is pronounced failed. Dynamic Web service selection is hence preferred in many scenarios and has been extensively studied in the past. However, there are relatively fewer works for dynamic Web service binding, especially using WS-BPEL as the composition language.
Previous works for dynamic Web service binding proposed using delegator or building an extension layer upon the original BPEL framework to handle dynamic Web service binding. However, most works assume that all candidate Web services have the same specification. In this thesis, we consider both heterogeneous Web service interfaces and dynamic Web service binding. To do so, we use WS-BPEL 2.0 extension activity for invoking a task. In addition, the set of candidate Web services for each task as well as conversion rules for interface mapping and data conversion have to be specified by the designer. Experimental results show that our approach has superior performance in terms of response time and reliability.

CHAPTER 1－Introduction 1
1.1 Background 1
1.2 Motivation 3
1.3 Thesis Organization 5
CHAPTER 2－Literature Review 6
2.1 Composition of Web services 6
2.1.1 WS-BPEL 2.0 and Extension Activity 6
2.1.2 Limitations of WS-BPEL 11
2.2 Dynamic Web service Selection and Binding 12
2.2.1 System Design for Dynamic Web service Selection and Binding 12
CHAPTER 3－Our Approach 18
3.1 System Architecture 18
3.2 Procedure for Designer 19
3.2.1 Design Stage 21
3.2.2 Deployment Stage 28
3.2.3 Runtime Stage 28
CHAPTER 4－Performance Evaluation 32
4.1 Experiment Design 32
4.1.1 Illustrating Example 33
4.1.2 System Implementation 40
4.2 Experimental Result and Comparison 41
CHAPTER 5－Conclusion 46
References 47
Appendix A－ Schema of WS Binding Specification 49

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