XML Basic-from w3schools.com_Asp.Net XML
日期：2008-07-27 浏览次数：20350 次
In our XML tutorial you will learn what XML is and the difference between XML and HTML. You will also learn how to start using XML in your applications.
Introduction to XML
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XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.
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What you should already know
Before you continue, you should have some basic understanding of the following:
WWW, HTML and the basics of building Web pages
Web scripting languages like javascript or VBScript
If you want to study these subjects first, before you start reading about XML, you can find the tutorials you need at W3Schools' Home Page.
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What is XML?
XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to describe data
XML tags are not predefined. You must define your own tags
XML uses a Document Type Definition (DTD) or an XML Schema to describe the data
XML with a DTD or XML Schema is designed to be self-descriptive
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The main difference between XML and HTML
XML was designed to carry data.
XML is not a replacement for HTML.
XML and HTML were designed with different goals:
XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.
HTML is about displaying information, while XML is about describing information.
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XML does not DO anything
XML was not designed to DO anything.
Maybe it is a little hard to understand, but XML does not DO anything. XML was created to structure, store and to send information.
The following example is a note to Tove from Jani, stored as XML:
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
The note has a header and a message body. It also has sender and receiver information. But still, this XML document does not DO anything. It is just pure information wrapped in XML tags. Someone must write a piece of software to send, receive or display it.
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XML is free and extensible
XML tags are not predefined. You must "invent" your own tags.
The tags used to mark up HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p>, <h1>, etc.).
XML allows the author to define his own tags and his own document structure.
The tags in the example above (like <to> and <from>) are not defined in any XML standard. These tags are "invented" by the author of the XML document.
--------------------------------------------------------------------------------
XML is a complement to HTML
XML is not a replacement for HTML.
It is important to understand that XML is not a replacement for HTML. In future Web development it is most likely that XML will be used
Introduction to XML
--------------------------------------------------------------------------------
XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.
--------------------------------------------------------------------------------
What you should already know
Before you continue, you should have some basic understanding of the following:
WWW, HTML and the basics of building Web pages
Web scripting languages like javascript or VBScript
If you want to study these subjects first, before you start reading about XML, you can find the tutorials you need at W3Schools' Home Page.
--------------------------------------------------------------------------------
What is XML?
XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to describe data
XML tags are not predefined. You must define your own tags
XML uses a Document Type Definition (DTD) or an XML Schema to describe the data
XML with a DTD or XML Schema is designed to be self-descriptive
--------------------------------------------------------------------------------
The main difference between XML and HTML
XML was designed to carry data.
XML is not a replacement for HTML.
XML and HTML were designed with different goals:
XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.
HTML is about displaying information, while XML is about describing information.
--------------------------------------------------------------------------------
XML does not DO anything
XML was not designed to DO anything.
Maybe it is a little hard to understand, but XML does not DO anything. XML was created to structure, store and to send information.
The following example is a note to Tove from Jani, stored as XML:
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
The note has a header and a message body. It also has sender and receiver information. But still, this XML document does not DO anything. It is just pure information wrapped in XML tags. Someone must write a piece of software to send, receive or display it.
--------------------------------------------------------------------------------
XML is free and extensible
XML tags are not predefined. You must "invent" your own tags.
The tags used to mark up HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p>, <h1>, etc.).
XML allows the author to define his own tags and his own document structure.
The tags in the example above (like <to> and <from>) are not defined in any XML standard. These tags are "invented" by the author of the XML document.
--------------------------------------------------------------------------------
XML is a complement to HTML
XML is not a replacement for HTML.
It is important to understand that XML is not a replacement for HTML. In future Web development it is most likely that XML will be used
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