網路服務規範被提出後，企業相繼投入開發各種網路服務，可供存取的網路服務大量增加，然而，也造成了下面兩個問題：網路服務提供者開發了許多種類的網路服務，但重複開發提供相同服務功能的網路服務，如何有效率地從眾多服務中檢索出所需網路服務成為重要的議題；此外，使用者的需求日趨複雜且多元，單一網路服務難以提供所有的需求，因此需要網路服務組合方法以因應此項問題。
以往組合運作需要流程建構者先行建構組合流程，依據流程中定義好的組合順序，搜尋符合條件的網路服務，因此，網路服務檢索在服務組合運算中扮演了重要的角色，以此方法進行服務組合需要人力介入。為了降低人力的需求，在組合網路服務時希望達到自動化，並且增加檢索率以滿足服務使用者請求，因此，使用語義資訊來進行可能的網路服務組合成為一個新興方法。語意網對網際網路中的資訊做了較為完善的定義，OWL-S是基於語義網規範而發展的網路服務描述文件，讓網路服務中的資料能夠被自動化程式或工具分享、理解並且處理，增加了實現網路服務自動化組合的可能性。在確保網路服務的可組合性時，需要比對網路服務的功能、輸入與輸出的連結性，比對時所有網路服務之間兩兩進行相容性計算，因此比對運算時間成為一大負擔。為減少運算時間，本研究提出一種分群方法，分別對網路服務的功能敘述(Description)及輸出(Output)進行分群，其中功能說明群聚過濾網路服務，而輸出群聚主要用於相容性計算，並以群組資料代替個別的網路服務運算，以降低比對計算量以及資料壓縮，然後使用回溯法(Backtracking Algorithm)進行網路服務的組合。
本研究提出分群式網路服務組合方法，並與Liu (2007)等學者之研究成果比較，由實驗發現本研究分群方法改善了檢索網路服務時效能，同時減短服務維護時間，也驗證了利用語意資訊能夠提升組合成效。

The enterprise developed various web services and the number of accessing web services rising rapidly. How to discovery the suitable web services becomes an important issue. Also, user’s requests become more complex. Single web service may not fulfill the user’s requests. Web services composition is a solution to overcome this problem. In the past, the compositing flow should be determined first. However, building the compositing flow requires human resource to participate in. so, automatic web services composition has been proposed to reduce the labor power. This goal can be achieved by finding linkable services with machine automatically understanding the semantics of web services. OWL-S description language, which supporting the automatic programs executing, has been proposed for semantic web.
In this paper, the compatibility of input and output between web services are sued for composing. However, existed methods spend much time due to the compatibility calculating is all-against-all. To overcome the problems mentioned above, a cluster-based service composition method according to the description and the output parameter is proposed. The compatibility process looks for the cluster of the linkable services rather than finding the web services straightly. It can decrease the time of calculating and compressing the information. Finally, the backtracking algorithm is adopted to compose the web services.
To verify the proposed approach, performance measurements are used. According to the results, the proposed approach not only alleviates users from time-consuming compositing tasks but also improves the effect of discovering.

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