Extending Public XHTML DTDs

In the previous section, I created a new DTD to extend XHTML, and I put it to work in an XHTML document like this:

<?xml version="1.0"?> 
<?xml-stylesheet type="text/css" href="ch17_19.css"?>
<!DOCTYPE html SYSTEM "ch17_17.dtd">
<html xmlns="ch17_17.dtd"
xml:lang="en" lang="en">
    <head>
        <title>
        </title>
    </head>

    <body>
        <p>
            This text uses a new XHTML element for
            <underlinedredtext>emphasis</underlinedredtext>.
        </p>
    </body>
</html>

In this case, I declared a local DTD for private use with the SYSTEM keyword. You can also make your DTD public with the PUBLIC keyword, but to do that, you've got to create a formal public identifier (FPI). Here are the rules for FPIs:

  • The first field in an FPI specifies the connection of ...

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