Processing Instruction: Difference between revisions

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An XML processing instruction is enclosed within <code><?</code> and <code>?></code>, and contains a ''target'' and optionally some content, which is the node value, that cannot contain the sequence <code>?></code>.<ref>{{cite book | title = The Internet encyclopedia, Volume 3 | url = https://archive.org/details/internetencyclop00bidg_359 | url-access = limited | author = Hossein Bidgoli | page = [https://archive.org/details/internetencyclop00bidg_359/page/n911 877] | publisher = John Wiley and Sons | year = 2004 | isbn = 0-471-22203-8}}</ref>

<sourcesyntaxhighlight lang="xml"><?PITarget PIContent?></sourcesyntaxhighlight>

The [[XHTML#XML declaration|XML Declaration]] at the beginning of an XML document (shown below) is '''not''' a processing instruction, however its similar syntax has often resulted in it being referred to as a processing instruction.<ref name="nutshell">{{cite book | title = XML in a nutshell | author = Elliotte Rusty Harold, W. Scott Means | isbn = 978-0-596-00764-5 | page = 23 }}</ref>

<sourcesyntaxhighlight lang="xml"><?xml version="1.0" encoding="UTF-8" ?></sourcesyntaxhighlight>

== Examples ==

The most common use of a processing instruction is to request the XML document be rendered using a [[Extensible Stylesheet Language|stylesheet]] using the 'xml-stylesheet' target, which was standardized in 1999.<ref>http://www.w3.org/TR/xml-stylesheet/</ref> It can be used for both [[XSLT]] and [[Cascading Style Sheet|CSS]] stylesheets.

<sourcesyntaxhighlight lang="xml"><?xml-stylesheet type="text/xsl" href="style.xsl"?></sourcesyntaxhighlight>

<sourcesyntaxhighlight lang="xml"><?xml-stylesheet type="text/css" href="style.css"?></sourcesyntaxhighlight>

The [[DocBook]] XSLT stylesheets understand a number of processing instructions to override the default behaviour.<ref>http://docbook.sourceforge.net/release/xsl/current/doc/pi/pi-fo.html</ref>