Research Background

Xml Model

“EXtensible Markup Language (XML), is a W3C Recommendation in 1998 for marking up data” (Bray et al., 2007). It is designed for publishing and exchanging a large scale of digital data over the Internet. It is a Markup language that is used to define the structure of information and its elements’ contents, where HTML is used to define the way in which the elements are displayed on a web page. It can also be considered as an ideal format for server-to-server transfer of structured data (Bansal and Alam, 2001).

The importance of XML documents transformation is largely increased. Moreover different XML models have common requirements and limitations as tools for data management. For rich data to be shared among different groups, all concepts need to be placed into a common frame of reference. XML schemas must be globally standardized among groups, or mapping must be created between all pairs of related data. Parsing and text conversion slows down the access of the data.

A well-formed XML document is one that corresponds to the XML 1.0 (Bray et al., 2007) grammar specified by W3C. It has exactly one root element, which is called document element. Each starting element tag should have a corresponding closing tag. The elements should be nested within one another. The tags and nesting rules allow XML to represent information in a hierarchical manner. Figure ‎1 shows an example for valid XML document.

In recent years, significant development in the XML domain has been achieved. Many languages based upon XML Markup have been designed; XML Schema and XML XQuery have been developed. These standardized technologies augment the data processing abilities of XML. The following sections give a brief description of a variety of XML based languages and technologies.

Figure 1.

An example of XML document

Xml Query Languages

XML query languages are used to enable the user to retrieve data from a single XML document using XPath language, or from multi-documents using XQuery language.