First knowledge of XML

XML XML is an identity language. An XML element consists of a start tag, an end tag, and data between tags. The start and end tags are used to describe the data between tags. The data between the labels is considered to be the value of the element. For example, in the following example of an XML element, the value of the element "student" is "Zhangrui".

<student>zhangrui</student>
The element name ("Student") allows you to mark the value "student" so that you can differentiate the data from other similar data.


The basic role of XML:

1. Used to transmit data

2. Establish a more effective and intuitive data structure, a tree structure, a full set of methods of operation of this structure

The 3.xml specification (or the actual point, XML parser) helps you to make sure that the strings you create are legitimate, and that there are ways to verify the legality

4. For the serve component that gets this string, you can manipulate it in an out-of-the-box way in XML, which is XPath, pattern, similar to a T-SQL statement. (but remember that XML is tree-structured)

5.XSLT transforms XML (similar to DTS) using XPath, one of the special cases is converting XML to HTML output.

The language of XML has its particularity. First of all, it must have its interpreter. There are currently two solutions,

DOM: We can access the DOM model of the document in a programming environment, and each element in the document becomes a node object in the tree structure, which makes it easy to traverse, add nodes, delete nodes, Modify nodes, and so on. We can already get XML parsers on most platforms, including Windows, UNIX, OS 400, MVS. Java parsers, such as IBM's XML4J (XML for Java) parser.

DTDs: Parsing of structured XML documents, directives, elements, entities, attributes, and so on in a document can be represented by an object model. The logical structure of the entire document resembles a tree, and the resulting object model is the node of the tree, each containing both methods and attributes.