透過全球資訊網搜尋所需的資料已經愈來愈普遍，但是，網路頻寬的擴充速度緩慢，造成使用者在資料的擷取上必須面臨更長的等待時間。透過代理伺服器可以有效降低一個區域網路的頻寬需求，並減少使用者瀏覽網頁時的回應時間。在代理伺服器擊中率普遍不高的情形下，使用者仍是需要時間來等待資料的抓取。另外，目前的代理伺服器無法提供動態改變服務政策來應付不同的使用需求和網路環境。
本系統綜合代理伺服器的特性，提供使用者訂閱網站的服務，藉由我們的系統把網站內容預先擷取回來存在代理伺服器的快取內，同時自動更新內容，確保使用者每次都能瀏覽到最新的資料。再加上使用者能動態地設定代理伺服器的服務政策，讓使用者選擇以瀏覽網頁的速度為優先政策還是以擷取最新的資料為優先政策。

World Wide Web makes information retrieval more and more convenient. People often spend too much time searching and browsing the Web due to insufficient network bandwidth. Web proxy server is used to reduce the network latency and bandwidth consumption. However, the hit ratio of a proxy server is generally low, hence users still often have to wait for retrieving information. Besides, the existing web proxy servers do not support users to dynamically change the service policy to fit the user’s requirements in term of response time and freshness of data.
In this thesis, we describe the design and implementation of a web proxy system that provides services for users to subscribe their favorite Web Pages. The subscribed Web Pages will be prefetched and kept in proxy’s cache space. The subscribed Web Pages will be refreshed automatically. Our proxy system also provides for users to dynamically change the service policy to fit their demand either for quick response or for getting the up-to-date data.

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