Introduction to XML-extensible Markup Language (extensible Markup Language)

(what) XML What is it?

XML refers to Extensible Markup Language (extensible Markup Language)

1, XML is a markup language, similar to HTML.

2. XML has a self-descriptive nature

3. XML is designed to transmit and data (design purpose/purpose)

The relationship and difference between XML and HTML

XML is a supplement to HTML, not a substitute.

Similarities: 1, both are markup languages. 2, are the recommended standard

Differences: 1, (the purpose of different) XML is designed to transmit and store data, focusing on the content of the data; HTML is designed to display data, focusing on the display of data. 2, (different tags) XML tags are not predefined, self-descriptive, need to define their own, HTML tags are predefined.

( why Why do you want to use XML ? --Application

• Separate the data from HTML, allowing the HTML to focus more on layout and display.

• Simplify data sharing and transfer data to and from incompatible systems.

( How ) How to use XML ? --Grammar rules

1. First define the declaration of the XML version

2. The document must have a root element

3. The element must have a close tag

4, the label is sensitive to the case

5. label must be nested correctly

6. Attribute values must be quoted

<?xml version= "1.0" encoding= "iso-8859-1"? ><note><to>george</to><from>john</ From>
　　
The first line is the XML declaration. It defines the version of the XML (1.0) and the encoding used (iso-8859-1 = latin-1/Western European character set).
The root element of the document is <note>
There are 4 sub-elements, namely <to> <from> 
Elements (regardless of the root element or child element) are closed and nested correctly.
Introduction to XML-extensible Markup Language (extensible Markup Language)