XML and its functions, CSS, XSL, XSLT, Dom, And sax concepts, XML schema and xpath

The following concepts are compiled after reading "no nonsense XML" and "XML manual version 4" in the Super Star PDG format

1. What is XML?
Extensible markup language, that isScalability Markup Language. A tag is an information symbol that a computer can understand. Through this tag, a computer can process various types of information. Article . To define these tags, you can either select an international markup language, such as HTML, or use a markup language that is freely determined by people like XML. This is the scalability of the language. XML is simplified and modified from SGML. It mainly uses XML, XSL, and XPath.
Understanding: Chinese idioms are the XML defined by the predecessors. idioms are the new marks created by future generations. As long as they are understood, they can be used and understood by others. We can imagine that XML only defines rules without restrictions on content. By comparing HTML, we can find that all the tags in HTML are pre-defined and cannot be added. As the author says,XML is the language of the design language.
The XML file is also a text file. The important point is that it canPassed as a string(Good)
HTML: hypertext markup language. It is a simple markup language used to create hypertext documents that can be transplanted from one platform to another. It is often used to create web pages. HTML files are embedded with format identifiers and text linksCodeText File

2. Advantages and functions
(1) information intercommunication (Exchange) in heterogeneous systems ). A heterogeneous system no longer needs to care about the data storage methods and operating systems used by the other party. You only need to use XML as the intermediary format. XML can easily convert the existing two-dimensional form of relational databases to XML format.
(2) simple and easy to save. Who can imagine that a document like word can be opened in 50 years? Who is willing to update all their documents every time the word editing software is upgraded? (It may be less ). XML text file? Simple. No.

3. xml tag (TAGS) or simple syntax
(1) statement, such as <? XML version = "1.0" encoding = "gb2312"?>; The XML version number, the character set used.
(2) elements (elements). elements at the highest level are called root elements or document elements. Each XML file must have only one element. Elements can be divided into simple elements and composite elements (with lower-level elements ).
(3) attributes can be included in an element (attributes)
 

4. What is a Cascading Style Sheet?
The description structure of the common flag language, rather than the format. The style sheet adds the display format without damaging the document structure.

5. What is XSL? What is the relationship with CSS? What is the relationship with XSLT?
The alternative to CSS is XSL (Extensible Stylesheet Language), which can be an extensible style single language. XML can be reproduced and output (for example, HTML) documents in any format through XSL subset XSLT (XML Conversion ).

6. What is Dom?
Document Object Model (Document Object Model), which is an API for standardized XML processing by W3C. This API has been implemented in Microsoft IE.

7. What is sax? What is the difference between Dom and sax?
Simape API for XML (simple xml api ).
The difference between Dom and sax: Let's take a look at this example: a m xml is located at the other end of the Internet. If you use Dom, you only have to wait until the data is finally obtained, it will fill the computer memory and hard disk space, and eventually occupy all space, and the system crashes .; The difference is that it uses the forward mode to gradually obtain data and can be terminated at any time;

8. What is XML schema?
The set of statements, expressed in data definition language, that completely describe the structure of a data base.
A set of statements expressed in Data Definition Language.Database Structure.

Equivalent to data table structure definition, including primary key, custom type, default value, etc.

9. What is XPath?
XML Path lanager is an XML tag used to query and filter text in XML documents.