Real-world information including subjective opinions and judgments need imprecise data to bemodeled for representation and querying in databases. The Extensible Markup Language (XML) hasbecome a de-facto standard for data modeling and exchange in recent years. Efforts on modelingimprecision and representing such data in XML have not been fully developed. In this paper, anXML based fuzzy data representation and querying system is presented. Complex and imprecisedata are represented using a fuzzy extension of XML. The representation forms the basis for asystem which enables fuzzy querying on XML documents using XQuery, a XML query language. The system also enables restructuring of XML Schemas through merging of elements of the XMLdocuments. By using this feature of the system, application specific XML Schema and XMLdocuments can be generated from the existing documents. Keywords'. Fuzzy query; XML; native XML databases.
1. Introduction
A database is an organized collection of data. Traditional database management systemsare particularly suited to represent crisp, well defined data using standard structures. However, real-world information includes subjective opinions and judgments that requirethe modeling of complex and imprecise data along with crisp data. The representation ofsuch uncertain and complex data in a database is still a research issue. The Extended NonFirst Normal Form (ExNF2) [1] data model is a model that has been proposed for therepresentation of such uncertain and imprecise data.
The Extensible Mark-up Language (XML) [2], [3], [4], [5] is widely used for datarepresentation and interchange. XML allows the separation of content and presentation, i.e., XML documents simply define the data representation and do not deal with thepresentation. XML can be used to represent complex and hierarchical information, whichare basic modeling constructs in the ExNF2 model.
This work is partially supported by the NSF Grant No. HRD-0401679, AHPCRC Contract No. DAAD19-01-2-0014 and ARL Contract No. DAAL01-98-2-0065. The content of this work does not reflect the position orpolicy of the sponsors and no official endorsement should be inferred. Choosing the most appropriate database management system to handle XML datadepends on the application and data structure. With increasingly large amount of databeing represented as XML documents, it becomes necessary to efficiently store and querythese XML documents. Native XML databases have several advantages over traditionaldatabase management systems in managing XML data. When the data is semi-structured, mapping it to a relational database results in either a large number of columns with nullvalues (which wastes space) or a large number of tables (which is inefficient). Anotherreason to store data in a native XML database is retrieva l speed. Depending on how thenative XML database physically stores data, it is possible to retrieve data much fasterthan a relational database. This is because the storage strategies used by native XMLdatabases store entire documents together physically or use physical (rather than logical) pointers between the parts of the document; permitting the documents to be retrievedeither without joins or with physical joins, both of which are faster than the logical joinsused by relational databases [11].




真實(shí)世界的信息，包括主觀的意見(jiàn)和判斷，需要不精確數(shù)據(jù)為藍(lán)本來(lái)表示并在數(shù)據(jù)庫(kù)中查詢(xún)。近年來(lái)，可擴(kuò)展標(biāo)記語(yǔ)言（XML）事實(shí)上已經(jīng)成為數(shù)據(jù)建模和交流的標(biāo)準(zhǔn)。在XML中，對(duì)不精確性的建模和代表這些數(shù)據(jù)做出的努力沒(méi)有得到充分發(fā)展。本文中，提出了基于XML的模糊數(shù)據(jù)表示和查詢(xún)系統(tǒng)。用模糊擴(kuò)展的XML來(lái)表示復(fù)雜和不精確的數(shù)據(jù)。這種表示法形成了一個(gè)基礎(chǔ)系統(tǒng)，能夠在XML文檔使用XML的一種查詢(xún)語(yǔ)言XQuery進(jìn)行模糊查詢(xún)。該系統(tǒng)還可以通過(guò)XML架構(gòu)重組，合并XML元素文件。通過(guò)使用此功能的系統(tǒng)，應(yīng)用程序特定的XML架構(gòu)和XML文件可以從現(xiàn)有的文件中產(chǎn)生。
關(guān)鍵字:模糊查詢(xún)，XML,原生XML數(shù)據(jù)庫(kù)。

1、簡(jiǎn)介
數(shù)據(jù)庫(kù)是數(shù)據(jù)的一個(gè)有組織的集合。傳統(tǒng)的數(shù)據(jù)庫(kù)管理系統(tǒng)特別適合于代表那些使用標(biāo)準(zhǔn)結(jié)構(gòu)的清晰、明確界定的數(shù)據(jù)，。然而，現(xiàn)實(shí)世界的信息，包括主觀的意見(jiàn)和判斷，需要復(fù)雜和不準(zhǔn)確的數(shù)據(jù)建模同時(shí)也需要明確界定的數(shù)據(jù)。在數(shù)據(jù)庫(kù)中代表這種不確定性和復(fù)雜的數(shù)據(jù)仍然是一個(gè)正在研究中的問(wèn)題。擴(kuò)展非第一范式（ExNF2）[1]數(shù)據(jù)模型是一個(gè)已為擬議的代表這種不確定和不精確數(shù)據(jù)模型。
可擴(kuò)展標(biāo)記語(yǔ)言（XML）[2][3][4][5]，被廣泛用于數(shù)據(jù)代表和交換。XML允許內(nèi)容和表現(xiàn)的分離，也就是說(shuō)，XML文檔簡(jiǎn)單定義了數(shù)據(jù)表示但是并不處理它的表現(xiàn)形式。XML可以用來(lái)表示復(fù)雜和層次性的信息，這是ExNF模型的基本造型結(jié)構(gòu)。
選擇最合適的數(shù)據(jù)庫(kù)管理系統(tǒng)，以處理基于應(yīng)用程序和數(shù)據(jù)結(jié)構(gòu)的XML數(shù)據(jù)。隨著越來(lái)越大的數(shù)據(jù)量作為XML文檔表示，有必要有效地存儲(chǔ)和查詢(xún)這些XML文檔。在管理XML數(shù)據(jù)中，原生的XML數(shù)據(jù)庫(kù)比傳統(tǒng)的數(shù)據(jù)庫(kù)管理系統(tǒng)具有幾個(gè)優(yōu)點(diǎn)。當(dāng)數(shù)據(jù)是半結(jié)構(gòu)化時(shí)，映射到一個(gè)關(guān)系數(shù)據(jù)庫(kù)結(jié)果中將導(dǎo)致大量的空列（浪費(fèi)空間）或大量的表（低效的）。另一個(gè)在原生XML數(shù)據(jù)庫(kù)存儲(chǔ)數(shù)據(jù)的原因是檢索速度。原生XML數(shù)據(jù)庫(kù)在物理存儲(chǔ)數(shù)據(jù)方面，檢索數(shù)據(jù)比關(guān)系型數(shù)據(jù)庫(kù)快得多。這是因?yàn)樵鶻ML運(yùn)用存儲(chǔ)策略存儲(chǔ)整個(gè)文件或在文件的各部分中使用物理（而不是邏輯）指針;..