Introduction to the background of XML (1) WEB page tool language

Like HTML, XML comes from StandardGeneralizedMarkupLanguage, a standard general Markup Language (SGML. Before the Web was invented, SGML already existed. As its name implies, SGML is a general language that describes document materials with tags. it contains a series of document type definitions (DTD for short ), the DTD defines the meaning of the tag, so the SGML syntax can be expanded. SGML is very large and not easy to learn and use. it is also very difficult to implement on a computer. In view of these factors, researchers at the European Centre for Nuclear Physics, the inventor of the Web, developed based on the context at the time (1. XML)

Like HTML, XML comes from Standard Generalized Markup Language (SGML. Before the Web was invented, SGML already existed. As its name implies, SGML is a general language that describes document materials with tags. it contains a series of document type definitions (DTD for short), DTD
I. Background of XML generation
Like HTML, XML comes from Standard Generalized Markup Language (SGML. Before the Web was invented, SGML already existed. As its name implies, SGML is a general language that describes document materials with tags. it contains a series of document type definitions (DTD for short ), the DTD defines the meaning of the tag, so the SGML syntax can be expanded. SGML is very large and not easy to learn and use. it is also very difficult to implement on a computer. In view of these factors, researchers at the European nuclear physics research center, the inventor of Web, proposed the HTML language based on the capabilities of computer technology at that time (1989.
HTML only uses a small part of the SGML tag. for example, HTML 3.2 defines 70 tags. To facilitate the implementation on the computer, HTML-defined tags are fixed, that is, HTML syntax cannot be extended and does not need to contain DTD. The fixed syntax of HTML makes it easy to learn and use. it is also very easy to develop HTML browsers on computers. Because of the simplicity of HTML, Web technology is moving from the computer industry to the whole society, to thousands of households, and the development of Web is booming.
In recent years, as Web applications become more and more widely used, people gradually feel that HTML is not enough, and the syntax of HTML is too simple, which seriously hinders the use of HTML to express complex forms. Although HTML has released a new version, it already has expressions such as scripts, tables, and frames, but it still cannot meet the increasing demand. On the other hand, over the past few years, the development of computer technology has been very rapid, and it has been able to achieve a much more complex Web browser than when HTML was originally created. Therefore, developing a new Web page language is both necessary, it is also possible.
Some people suggest using SGML directly as the Web language, which can solve the difficulties encountered by HTML. However, SGML is too large for users to learn and use it easily. it is very difficult to fully implement the SGML browser, so they naturally think of using only the subset of SGML, make the new language easy to use and implement. In this situation, the W3C of the Web standardization organization recommends that you use a simplified SGML version-XML.

The preceding section describes the background of the WEB page tool Language XML (1). For more information, see other related articles in the first PHP community!