The XML is considered as the very special language which is capable to label the information content. The data from the structured and semi structured documents can be labeled in this way. The query languages are capable to display the intelligent use of these XML comfortably. In this way the queries can be employed across all sorts of data. The data which are physically stored in XML and stores as XML can be utilized in this way. The language which satisfies these specifications is generally known as XQuery languages. Thus these Query languages
XML is a markup language for structured documentation. Structured documents are documents that contain both content (words, pictures, etc.) and some indication of what role that content plays (for example, content in a section heading has a different meaning from content in a footnote, which means something different than content in a figure caption, etc.). Almost all documents have some structure.
A markup language is a mechanism to identify structures in a document. The XML specification defines a standard way of adding markup to documents.
So XML
XML is a versatile markup language, capable of labeling the information content of diverse data sources including structured and semi-structured documents, relational databases, and object repositories. A query language that uses the structure of XML intelligently can express queries across all these kinds of data, whether physically stored in XML or viewed as XML via middleware. This specification describes a query language called XQuery, which is designed to be broadly applicable across many types of XML data sources.
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In order to appreciate XML, it is important to understand why it was created. XML was created so that richly structured documents could be used over the web. The only viable alternatives, HTML and SGML, are not practical for this purpose.
HTML, as we've already discussed, comes bound with a set of semantics and does not provide arbitrary structure.
SGML provides arbitrary structure, but is too difficult to implement just for a web browser. Full SGML systems solve large, complex problems that
Abstract :
XML is an extremely versatile markup language, capable of labeling the information content of diverse data sources including structured and semi-structured documents, relational databases, and object repositories. A query language of similar versatility is needed to realize the potential of XML as a universal medium for data interchange. Most existing proposals for XML query languages are robust for particular types of data sources but weak for other types. In this paper, the authors combine features from several sources to propose a new
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