在網路科技發達的今日，網路服務逐漸已成為了組織間之商業流程整合的標準協定。透過網路服務的各項標準，組織可以快速地組裝其內部的網路服務以應對外部環境的變動。更重要的是，組織間可以透過分享其網路服務以進行跨組織的商業流程整合與溝通。一般而言，網路服務的組裝的方式可分為兩種- Orchestration 與 Choreography。 Orchestration 主要應用於單一流程的建立與組合，組織內外部的網路服務可以透過此方法進行整合、調整與溝通。 相對而言，Choreography則用於跨組織的溝通與流程整合。在Choreography 環境中，各個網路服務皆為一獨立個體，且各個網路服務可以自主的選擇與啟用其它網路服務以完成其工作。 在Choreography環境中，各個網路服務之間是否能夠互相搭配與整合是一個相當重要的議題。因此，我們研究如何在Choreography環境中透過資訊的分享以提高整體商業流程的成功率。在我們的方法中，每一個網路服務皆可透過一個固定之機制來宣告與分享其服務之行為與需求，且各個服務可透過其夥伴服務所提供之資訊建立一個局部視圖以指導其服務內部各項作業之運作。本研究之實驗與評估的方法為，在不同網路服務的可用性下分別進行100,000次的模擬執行以評估各個方法的成功率。實驗結果顯示，我們所提出的方法確實能有效的提高整體商業流程的成功率。

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 π-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.

Abstract ii
中文摘要 iii
CHAPTER 1 – Introduction 1
1.1 Background 1
1.2 Motivation 2
1.3 Thesis Organization 6
CHAPTER 2 Literature Review 7
2.1 Web Service Technologies 7
2.1.1 SOAP 8
2.1.2 WSDL 9
2.2 Orchestration and Choreography 10
2.2.1 Orchestration 10
2.2.2 Choreography 11
2.3 Web Service Composition 12
2.4 Web Service Selection 13
2.5 Theoretical Process Models 15
2.5.1 Finite State Machine 15
2.5.2 Petri Net 16
2.5.3 The π- Calculus 16
CHAPTER 3 Choreography Model and Problem Definition 21
3.1 Using π-calculus for Modeling Web Services 21
3.1.1 Basic Operation 21
3.1.2 Structural Activities 23
3.1.3 Sequential Composition 24
3.1.4 Alternative Composition 25
3.1.5 Repeat-Until Composition 27
3.1.6 While Loop 28
3.1.7 Parallel Composition 29
3.2 Composability Checking 31
3.3 Choreography model 35
3.4 An Illustrating Example 37
3.5 Problem Description 42
CHAPTER 4 The Method 44
4.1 Architecture 44
4.2 Generating Viewc for Service Consumer 46
4.2.1 General Case 48
4.2.2 Multiple Instances Case 56
4.3 Generating Viewp for Service Provider 58
4.4 Building Local Composition 59
CHAPTER 5 Performance Evaluation 65
5.1 Experimental Design 67
5.2 Success Rates of Four Methods 69
5.2 The Influence of Partner-Hierarchy 73
5.3 The Influence of Transitive Callback 78
5.4 The Scenario of Multiple Instance Case 82
CHAPTER 6 Conclusion 87
Reference 89

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