行動代理者 (Mobile agent) 是可在一異質網路系統 (Heterogeneous network system) 內從一主機 (Host) 遷移 (Migrate) 至另一主機併和其他代理者及分散資源系統(Distributed resources) 溝通及交互作用(Interact)之軟體程式。它們特別適合用來發展分散式及網路上的應用系統。

　　由於行動代理者被發送到行動代理者網路執行工作時，常常會與使用者或其他行動代理者通訊，來完成使用者所交待的工作，而要與行動代理者通訊，我們必須知道行動代理者的所在位置，由於行動代理者的移動具備有自主性(autonomy)，因此行動代理者的所在位置為不可預測的，所以我們需要一套搜尋機制來得到行動代理者的所在位置。

　　本篇論文主要提出一個具一般性且有效率的行動代理者搜尋機制 (Hybrid-Proxy)， 本機制參考行動代理者搜尋機制中著名的兩個方法，Home-Proxy和Forward-Proxy的方法，設計一套系統以擷取兩個方法之優點、以互補其各自之缺點，並利用叢集式拓樸的叢集概念(Cluster Concept)來協助行動代理者在移動時選擇所留的移動資訊為位置資訊(location update message)或是足跡資訊(forward point)，當想要與某ㄧ行動代理者通訊的使用者或是其他行動代理者，便可根據行動代理者所留下的移動資訊，尋跡找到該行動代理者。

　　本文另實作出一個模擬器，模擬真實行動代理者執行環境會發生的事件，然後實行三種搜尋機制，以蒐集模擬的結果來比較三種機制的優劣，並分出析本文所提出的搜尋機制適用於何種情形。

　　Mobile agents are software programs that can move from host to host and interact with other agents and distributed resources in a heterogeneous network. They are therefore particularly effective for developing distributed applications. Mobile computing is also gaining more and more popularity in the recent years as professionals discover the benefits of being able to connect to the vast of distributed information resources at all times without any spatial constraints.

　　After a mobile agent is launched for remote operations, it often needs to communicate with his owner user or other mobile agents to accomplish the jobs scheduled by its owner. On the other hand, when the owner of a mobile agent needs to communicate with the mobile agent, he needs to track down the mobile agent in order to send it messages. Since mobile agents move autonomously, it is hard to predict the latest location of a mobile agent. That is why a mobile agent searching mechanism is crucial to the communication mechanism of a mobile agent system.

　　This thesis proposes a mobile agent searching mechanism with generality and efficient. Named Hybrid-Proxy searching mechanism, it takes advantages from both the Home-Proxy and Forward-Proxy searching mechanisms but excludes their major deficiencies. It also uses the cluster concept to help the mobile agent on deciding which kind of information, location update message or forward point, should be left over as movement information when they move. When the users or the other mobile agents need to communicate with a mobile agent, they track down the mobile agent according the movement information it left.

　　This research also develops a simulator to simulate an entire mobile agent working environment. The three mechanism are all evaluated by this simulator to compare their performance and to find out in what conditions the mechanism performs better.

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