Comments

XML comments are very much like HTML comments. You can use comments to include explanatory notes in your document that are ignored by XML parsers; comments may appear anywhere in a document outside other markup. As in HTML, you start a comment with <!-- and end it with --> . Here's an example:

 <?xml version="1.0" encoding="UTF-8"?>  <DOCUMENT>  <!--Start the document off with a greeting.-->   <GREETING>   <!--Here's the greeting's text.-->  Hello from XML!     </GREETING> </DOCUMENT> 

You should follow a few rules when adding comments to an XML document:

Comments must not come before an XML declaration. For example, this is incorrect:

  <!--Here's my document.-->  <?xml version="1.0" encoding="UTF-8"?> <DOCUMENT>     <GREETING>         Hello from XML!     </GREETING> </DOCUMENT> 

You can't put a comment inside markup, like this:

 <?xml version="1.0" encoding="UTF-8"?>  <DOCUMENT <!--Start the document-->>  <GREETING>         Hello from XML!     </GREETING> </DOCUMENT> 

You cannot use -- inside a comment because XML parsers look for that string within a comment as indicating the end of the comment. For example, this is incorrect:

 <?xml version="1.0" encoding="UTF-8"?>  <DOCUMENT>  <!--Start the document off--politely--with a greeting.-->  <GREETING>         Hello from XML!     </GREETING> </DOCUMENT> 

You can also use comments to remove parts of documents as far as a parser is concerned . For example, here I'm commenting out the <MESSAGE> element:

 <?xml version="1.0" encoding="UTF-8"?>  <DOCUMENT>     <GREETING>         Hello From XML     </GREETING>  <!--   <MESSAGE>   Welcome to the wild and woolly world of XML.   </MESSAGE>   -->  </DOCUMENT> 

Here's how a parser treats this document:

 <?xml version="1.0" encoding="UTF-8"?>  <DOCUMENT>     <GREETING>         Hello From XML     </GREETING> </DOCUMENT> 


Real World XML
Real World XML (2nd Edition)
ISBN: 0735712867
EAN: 2147483647
Year: 2005
Pages: 440
Authors: Steve Holzner

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