分散式系統具有資源共享及運算更有效率等優點，使得分散式系統的應用越來越廣泛，有關分散式系統的研究也越受重視。一些存在分散式系統中的不正常現象，如：死結(deadlock)，饑餓(stravation)，及臨界競賽(critical race)往往會抵消掉資源共享的好處並且容易產生通訊(communication)的錯誤，另外，保證一分散系統中行程(process)均能正確的執行終止(termination)也是一項值得研究的重要課題。 　　本篇論文將就分散系統中的死結、饑餓、臨界競賽及中止等問題之過去的文獻提出討論，並分別比較優、缺點，最後列出一些尚未解決及值得深入研究的問題。 / There are some addvantages of distributed systems, such as resources sharing and computing efficiency. Thus, the applications of distributed systems are more prevalent. The research of distributed systems had got great worth. Some undesired or abcdrmal behaviors such as deadlock, starvation, and critical race exist in distributed systems, which often offset the advantages of resources sharing and are prone to communication errors. It is very important to guarantee the processes of a distributed system which can terminate finitely. 　　In this thesis, we'll have thorough discussions and comparisons of those four properties through literature survey and then point out some unsolved problems at last.

雲端運算是近來全世界最熱門的資訊議題，任何設備只要能夠連上網路，就可以享有各種不同的網路服務，這些服務可能建置在不同的機器設備上，甚至可能在相隔遙遠的雲端裡，因此也稱之為雲端服務，在操作過程中，使用者不需要擔心服務安裝在哪裡，亦不用擔心服務如何達成，可想而知網路服務的背後，隱藏著很複雜的技術與架構。 網路服務的開發方式相當地簡單且快速，為系統帶來更大的便利與彈性，不過在管理的部份，卻變得越來越複雜，例如不易瞭解網路的結構與狀態、潛在的無窮迴圈及冗餘的流程問題，甚至是在資源共享的情況下，因等待或其他因素而導致死結的情況產生。這些問題將使得網路服務組合在執行時期，可能發生無法預期的錯誤。情況嚴重時，系統可能會完全鎖死或停止，對公司將造成重大的財務及商譽上的損失。這些流程的問題，需要在網路服務組合執行前先進行驗證，本研究透過流程轉換成派翠網路的分析，以確保流程設計的正確性與穩定性。 因此，本論文運用網路服務標準，將雲端服務轉換成派翠網路模型，再以派翠網路中的針織法為分析基礎，檢驗模型的狀態，避免死結發生，並提供網路特徵報告書，以降低管理的複雜度，進而提升服務的穩定性。 / Cloud computing is regarded as the most popular recent ICT topic. Any equipment which can be connected to Internet can provide its user have the access to the various services, which may be built on different machines, or even may exist in the distant 'clouds' far away. However, in the operating process, the user has no need to worry where the service locates, needless to say how the service operates, which means that a considerably amount of data and techniques hide behind the Web service. Web service is an artifical piece of art, the user and the manager can concatenate several Web services online into a bigger one according to the conditions they need, which is a considerably simple and fast developing method bringing more convenience and flexibility for the system. Nonetheless, the managerial part also becomes more complex in problems like potential infinite loops and abundant procedures, for instance. What is worse is under the circumstance of resource sharing, the deadlocks happen while pending or other factors occur. These issues will lead to severe errors while the Web service compound operates. If the system completely locks and stops, serious financial damage and loss of commercial reputation will be caused to the company. Hence the design of procedures needs to be validated and transformed as Petri Net analysis before the Web service compound operates in order to assure the accuracy and stability of the procedure design. Therefore, this paper uses Web service standards, turning Web services into Petri Net models with knitting technique as analytical base, to validate the accuracy and stability of the model to avoid deadlock to happen in order to enhance the reliability of the service.