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  • 學位論文

多人環境下動態存取XML文件之並行控制機制研究

A Study of Dynamic Access XML Documents with Concurrency Control for Multi-User Environments

指導教授 : 陳靖國
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摘要


由於跨國企業的出現,企業的分公司之間或是企業之間常需要交換資訊以進行商業交易。XML文件因為具有使用者自行定義文件規格的特色而成為目前儲存資料的主流媒介。管理大量XML文件如果使用傳統檔案系統,可能導致資料重複發生、同步更新困難等問題,所以最好選擇資料庫管理系統來管理XML文件。當不同的使用者要同時存取同樣一份XML文件時,有適當的並行控制(Concurrency control)處理,以防止不可預期的錯誤發生。 目前針對XML文件設計的並行控制方法或協定(Protocol)中,普遍存在一些缺失,例如一個操作(Operation)中使用過多的鎖(Lock),複雜的協定(Protocol),或是缺乏詳細明確的演算法(Algorithm),造成理解與實做上的困難。本研究提出一套明確的並行控制演算法,可以讓多人同時對一份XML文件做搜尋、新增、修改、與刪除等四個常用的操作。搜尋演算法使用關鍵字搜尋方式,可輕易快速地找到相關資料,且只用一種鎖,亦即分享鎖(Share-lock)即可完成。新增、修改、或刪除演算法,配合路徑(Path)概念以及異動單元的使用,可以快速異動相關的資料,而且只用到兩種鎖,即分享鎖與互斥鎖(Exclusive-lock)而已。另外對資料的鎖定與釋放的處理,採用常見的成對鎖定(Lock-coupling)協定,使已鎖住的資料單元在不使用時可以儘早解開,以提升資料庫系統的操作執行並行度(Degree of concurrency)。

並列摘要


For business transactions, it is needed to have data exchange among enterprises or branches of a transnational corporation. XML (eXtensible Markup Language) is popular for data storage because XML allows the user to define the structure of an XML document. If the traditional file system is used to manage mass XML documents, the problems such as, data redundancy, concurrent update, may happn. It is better to manage XML documents with a database management system under concurrency control to avoid the occurrence of unpredictable errors. The concurrency control methods or protocols designed for XML, have some disadvomtages to realize and perform, such as too many lock types is used in an operation, some protocols are too complex to understand, or algorithms are not detailed. Our research proposes a set of explicit concurrency control algorithms for many user to do search, insertion, modification, and deletion operations on the same XML document. Our search method uses keyword search to find out the proper element data easily with only the share lock. Associated with a path and a specific unit, the insertion, modification, or deletion algorithms can update the specific unit with only two lock types, share lock and execution lock. The lock-coupling protocol is used to perform the lock and unlock actions of a node. A data item is unlocked immediately after it would not be used, to increase the degree of concurrency of operation execution.

參考文獻


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