Parsing, Creating, and Transforming XML Documents - Beginning Java 7 - page 912

in frying pan with one margarine-smeared side in
contact with pan. Fry for a
couple of minutes and flip. Fry other side for a
minute and serve.
</r:instructions>
</p>
</r:recipe>
</body>
</html>
Listing 10-6 specifies a default namespace for the XHTML language. No XHTML
elementtagneedstobeprefixedwith h: .However,recipelanguageelementtagsmust
still be prefixed with the r: prefix.
Comments and Processing Instructions
XMLdocumentscancontaincomments,whicharecharactersequencesbeginningwith
<!-- andendingwith --> .Forexample,youmightplace <!-- Todo --> in List-
ing10-3 ' s body elementtoremindyourselfthatyouneedtofinishcodingthiselement.
Commentsareusedtoclarifyportionsofadocument.Theycanappearanywhereafter
theXMLdeclarationexceptwithintags,cannotbenested,cannotcontainadoublehy-
phen( -- )becausedoingsomightconfuseanXMLparserthatthecommenthasbeen
closed,shouldnotcontainahyphen( - )forthesamereason,andaretypicallyignored
during processing. Comments are not content.
XML also permits processing instructions to be present. A processing instruction
is an instruction that is made available to the application parsing the document. The
instruction begins with <? and ends with ?> . The <? prefix is followed by a name
known as the target . This name typically identifies the application to which the pro-
cessing instruction is intended. The rest of the processing instruction contains text
in a format appropriate to the application. Two examples of processing instructions
are <?xml-stylesheet href="modern.xsl" type="text/xml"?> (as-
sociate an eXtensible Stylesheet Language [XSL] style sheet [see ht-
tp://en.wikipedia.org/wiki/XSL ] withanXMLdocument)and <?php /*
PHP code */ ?> (passaPHPcodefragmenttotheapplication).AlthoughtheXML
declaration looks like a processing instruction, this is not the case.
Note The XML declaration is not a processing instruction.