網路服務選擇問題主要在於如何選擇網路服務，以滿足使用者非功能性或服務品質的需求，在過去被廣泛的研究。這些研究大多討論服務品質的問題，包含可靠性、回應時間、執行成本等等。然而目前在先前的研究中，執行結果則沒有被提出來討論。在我們的研究中，我們提出了一個方法來做為網路服務選擇的依據，目的是滿足使用者對於執行結果的偏好。除此之外，我們也考慮網路服務之間的合作夥伴關係。網路服務之間的合作夥伴關係可能帶來更有利的執行結果，例如更好的品質或折扣。在我們的方法中，我們利用貝氏網絡來幫助我們選擇網路服務。我們提出一個例子，稱為旅遊規劃流程。根據旅遊規劃流程，我們建立了一個貝氏網絡的結構。我們提出了以貝氏網絡為基礎的網路服務選擇方法：合作夥伴優先貝氏網路(Partner-first Bayesian Network)和機率優先貝氏網路(Probability-first Bayesian Network)。這兩種方法在選擇網路服務時，都會考慮使用者的偏好、用戶輸入的變數，以及在流程中被選擇的網路服務。從實驗結果可以看出，貝氏網路相較於隨機選擇法(Random method)以及貪婪選擇法(Greedy method)，有更好的表現。

Web service selection problem focuses on how to choose component Web services to satisfy user’s non-functional (or QoS) need, and it has been extensively studied in the past. The QoS measures include reliability, response time, and execution cost. However, in some applications, execution result, as demonstrated on some output values, matters, and this is seldom addressed by previous researches. In our work, we proposed an approach to guide the WS selection with the goal to meet user’s preferences on the composition execution outcome. In addition, we consider the partner relationship between Web services. Some partner Web services may produce more desired execution result, such as better quality or a discount, than others. In our approach, we use Bayesian Network to guide Web services selection. Specifically, we propose two Bayesian Network-based methods: Partner-first Bayesian Network and Probability-first Bayesian Network. Both methods rank Web services by considering user’s preference, user’s input variables, and the past execution results of Web services. The experiment result shows that the proposed Bayesian Network methods perform better than the other more straightforward methods.

CHAPTER 1 – Introduction 1
1.1 Background 1
1.2 Motivation 2
CHAPTER 2 – Literature Review 6
2.1 WSs technologies 6
2.1.1 SOAP 6
2.1.2 WSDL 7
2.1.3 UDDI 9
2.2 WS Selection 9
2.3 Automatic Web services composition 11
2.4 Bayesian Network 12
CHAPTER 3 – Our Approach 15
3.1 An Illustrating Example 15
3.2 Our Approach 21
3.2.1. Bayesian Network Model 21
3.2.2. Handling Request Arrivals 25
CHAPTER 4 –Performance Evaluation 28
4.1 Experimental Design 28
4.2 Result of Success Rate 40
4.3 Result of Partner Rate 45
CHAPTER 5 – Conclusion 49

References

Ben-Gal, I. (2008). Bayesian Networks Encyclopedia of Statistics in Quality and Reliability: John Wiley & Sons, Ltd.
Christensen, E., Curbera, F., Meredith, G., & Weerawarana, S. (2001). Web Services Description Language (WSDL) 1.1.
Clement, L., Hately, A., Riegen, C. v., & Rogers, T. (2004). UDDI Spec Technical Committee Draft.
Darwiche, A. (2010). Bayesian networks. Commun. ACM, 53(12), 80-90.
Grassi, V., & Patella, S. (2006). Reliability prediction for service-oriented computing environments. IEEE Internet Computing, 10(3), 43-49.
Hwang, S.-Y., Lim, E.-P., Lee, C.-H., & Chen, C.-H. (2008). Dynamic Web service selection for reliable Web service composition. Services Computing, IEEE Transactions on, 1(2), 104-116.
Lee, K., Jeon, J., Lee, W., Jeong, S.-H., & Park, S.-W. (2003). QoS for Web services: requirements and possible approaches.
Majithia, S., Walker, D., & Gray, W. (2004). A framework for automated service composition in service-oriented architectures. In C. Bussler, J. Davies, D. Fensel & R. Studer (Eds.), The Semantic Web: Research and Applications (Vol. 3053, pp. 269-283): Springer Berlin / Heidelberg.
Menasce, D. A. (2002). QoS issues in Web services. Internet Computing, IEEE, 6(6), 72-75.
Mitra, N., & Lafon, Y. (2007). SOAP Version 1.2 Part 0: Primer (Second Edition).
Narayanan, S., & McIlraith, S. A. (2002). Simulation, verification and automated composition of web services. Paper presented at the Proceedings of the 11th international conference on World Wide Web.
Pourret, O., Naim, P., & Marcot, B. (2008). Bayesian networks: a practical guide to applications: John Wiley.
Rao, J., & Su, X. (2004). A survey of automated web service composition methods. Paper presented at the First International Workshop, SWSWPC 2004, San Diego, CA, USA.
Sirin, E., Parsia, B., Wu, D., Hendler, J., & Nau, D. (2004). HTN planning for Web Service composition using SHOP2. Web Semantics: Science, Services and Agents on the World Wide Web, 1(4), 377-396.
Wu, D., Sirin, E., Hendler, J., Nau, D., & Parsia, B. (2003). Automatic web services composition using SHOP2. Paper presented at the In Proceedings of Planning for Web Services Workshop in ICAPS 2003, Trento, Italy.
Wu, J., Liang, Q., & Jian, H. (2009). Bayesian network based services recommendation.
Yu, T., Zhang, Y., & Lin, K.-J. (2007). Efficient algorithms for Web services selection with end-to-end QoS constraints. ACM Transactions on the Web (TWEB), 1(1), 6.
Zeng, L., Benatallah, B., Dumas, M., Kalagnanam, J., & Sheng, Q. Z. (2003). Quality driven web services composition. Paper presented at the Proceedings of the 12th international conference on World Wide Web.
Zeng, L., Benatallah, B., Ngu, A. H. H., Dumas, M., Kalagnanam, J., & Chang, H. (2004). QoS-aware middleware for Web services composition. Software Engineering, IEEE Transactions on, 30(5), 311-327.
Zhao, H., & Doshi, P. (2009). A hierarchical framework for logical composition of web services. Service Oriented Computing and Applications, 3(4), 285-306.