2nd day: What is namespaces _ Basic Tutorial

After the DOCTYPE is declared, the following code is:

Usually the code we HTML4.0 is just, what is the "xmlns" here?

This "xmlns" is an abbreviation for XHTML namespace, called the "namespace" declaration. What is the role of namespaces? Ateptsevo's own understanding is:

Because XML allows you to define your own identity, the identities you define may be the same as those defined by others, but they represent different meanings. Errors are easily generated when files are exchanged or shared. To avoid this error, XML uses namespace declarations, allowing you to identify your identity through a URL point. For example:

Xiao Wang and Xiao Li have defined an identity, if Xiao Wang's name space is "http://www.xiaowang.com", Xiao Li's namespace is "http://www.xiaoli.com", then when the two documents exchanged data, will not confuse the identity , because it belongs to different namespaces.

A more popular explanation is that namespaces are a sign of a document that tells people who the document belongs to. But this "who" used a URL instead.

XHTML is an identity language in which HTML transitions to XML, which need to conform to the rules of the XML document, and therefore also need to define namespaces. And because XHTML1.0 can not customize the identity, so its namespace is the same, that is, "http://www.w3.org/1999/xhtml". It doesn't matter if you don't understand it, we just need to copy the code at this stage.

After the lang= "gb2312", specify your document in Simplified Chinese

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