Understanding Web page Tools Language XML (ii) definition

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Second, the definition of XML

XML is a condensed SGML that combines the richness of SGML with the ease of use of HTML in Web applications. XML retains the extensible functionality of SGML, which makes XML fundamentally different from HTML. XML is much more powerful than HTML, it is no longer a fixed tag, but allows the definition of an unlimited number of tags to describe the data in the document, allowing nested information structures. HTML is just a common way to display data on the Web, and XML provides a common way to process Web data directly. HTML focuses on the display format of Web pages, while XML focuses on the content of Web pages.

XML includes extensible Format Language XSL (extensible Style Language) and Extensible Link language xll (extensible linking Language).

XSL is used to translate XML data into HTML or other format languages. XSL provides a feature of overlapping page CSS that enables developers to construct web pages with an expression layer structure to differentiate them from XML data structures. XSL can also construct overlapping pages with HTML. XSL can explain an unlimited number of tags, which makes the Web layout more colorful, such as dynamic text, horse-style text. In addition, XSL also handles the multilingual, double-byte display of Chinese characters, the various processing of grids, etc.

XLL is a linked language of XML that is similar to HTML, but has a more powerful function. XLL supports scalable links and multiple directional links. It broke the HTML only support hypertext concept of the simplest link restrictions, can support the domain name independent of the address, two-way links, loops, multiple sources of collection links. XLL links are not subject to document constraints and are specified and managed exactly as required by the user.

To make XML easy to use, XML streamlines the functionality that is rarely used in SGML. Just as hundreds of thousands of of Chinese characters are commonly used in only 8,000, SGML's commonly used part only accounts for 20%,xml's abandonment of the less-common parts of SGML, making it leaner by 80%. As a result, the XML syntax specification is only 30 pages, while SGML has 500 pages.

XML design also takes into account its ease of use, ease of use from two aspects: on the one hand, users write Web pages convenient, on the other hand, designers to implement XML browser is not too difficult.

In summary, XML uses a simple and flexible standard format that provides a useful means of describing data and exchanging data for web-based applications. HTML describes a common way to display global data, and XML provides a common way to process global data directly.