資訊科技的發展日新月異，網際網路已經和日常生活密不可分，透過網路所提供的服務來進行軟體開發也愈來愈常見。但是這些由第三方(third-party)所提供的服務可能不具保障，軟體開發者有可能因為使用了這些不具保障的第三方服務而受到不可預期的影響。當然軟體開發者也可以尋求其它服務來替代，但是如果該服務無可取代，軟體開發者也只能束手無策。
　　本研究為了協助分散式運算環境(Distributed Computing Environment)下的軟體開發者，提出了服務合約(Service Contract)的構想。透過服務合約的訂定，期望能改善分散式運算架構中，軟體開發裡目前仍顯不足的例外處理機制(Exception Handling Mechanism)。我們針對分散式運算環境下例外處理機制無法跨平台或是跨網路的問題，利用code injection 的實作來說明服務合約和合約例外處理(Contract Exception Handling)的有效以及可行性。

Nowadays, software technology is making progress rapidly. Internet has become essential from everyday life and services provided via internet, such as web services, have become more and more common. However, services provided by third-party may not be trustworthy and reliable. Software that uses third-party service may encounter unexpected failures or errors. Unless the services are replaceable, software developers seem not have choices in trusting these third-party services.
To assist programmers that develop applications over web services, a service contract concept is proposed in this thesis. We believe that the exception handling mechanism in current programming language is inadequate and can be improved by contract. The contact is implemented by program instrumentation. It is transparent to the software developers.

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