What is XML, what can it do? --To the XML starter

XML can extend the markup language (extensible Markup Language). Mark refers to the computer can understand the information symbols, through this kind of mark, the computer can handle all kinds of information including articles. How to define these tags, you can choose either an international markup language, such as HTML, or a markup language that is freely determined by the person concerned, such as XML, which is the extensibility of the language. XML is simplified and modified from SGML. The main uses are XML, XSL, and XPath.

The above paragraph is a basic definition of XML, a widely accepted description. Simply put, XML is a descriptive language of data, although it is a language, but in general it does not have the basic function of a common language-it is recognized and run by the computer. Only rely on another language to explain it so that it achieves the desired effect or is accepted by the computer.

If you're new to XML, you might not be able to define what XML is. Perhaps you can look at what XML is, from the application side, and what you can do to understand it from XML, which should be more helpful than the more empty definition.

There are two main types of XML application surface, document type and data type. Here are a few common XML applications:

1, custom xml+xslt=>html, one of the most common document-type applications. XML stores the XML data for the entire document, and then XSLT transforms, parses, and combines the HTML tags in XSLT, which eventually becomes HTML, and is displayed on the browser. A typical example is the post on CSDN.

2, XML as a micro-database, this is one of the most common data-type applications. We use the relevant XML APIs (MSXML DOM, JAVA DOM, and so on) to access and query XML. In the implementation of the message board, you can often see XML as a database. At the same time, here to tell some new, database and database systems, the two concepts are different. By the way, here's how XML affects the database system. In a new version of the traditional database system, XML becomes a data type. and "traditional" is a new form of database, completely based on XML-related technology database system. At present, more well-known exist.

3, as the carrier of information transmission. Why is it the carrier? Because these applications are still based on XML as the basic form, but have developed a specific meaning of the format form. The most typical is the web SERVICE, which wraps the data into XML, but the XML here already has a specific specification, soap. But here it is also said that Ajax,ajax's application, is believed to have a part of the application of the custom XML as data, but did not become an industrial standard, here do not elaborate.

4, the application configuration information data. The most typical is the web.xml used to configure the Web server. This application is estimated to be easy to understand. All we need to do is store the data in XML and then run the load in our application, and then do the corresponding operations based on different data. Here in fact and application 2, a bit similar, the difference is that the data in the database change is a normal, and configuration information is often more static, lack of change.

5, some other documents in the XML format. such as Word, Excel, and so on.

6. Save the mapping relationship between the data. such as Hibernate.

In these common applications, we can also be divided into: custom XML and specific meaning XML according to its extensive application. The 1 and 2 are the categories of custom XML, and 3 to 6 are of particular meaning XML, or an extension of XML.

The 6 applications described here basically cover the main uses of XML. In short, XML is an abstract language, which is not as specific as the traditional programming language. To understand it in depth, you should start with its application, choose a purpose you need, and then learn how to use it.

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Author: Sank Orange