"Evaluation of XPath Expressions" section of JAXP 1.3 spec
 for context item evaluation,
 variable, function and QName resolution and return type conversion.</p>

 <p>If <code>source</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p><DD><DL>
<DT><B>Specified by: </B><DD><A HREF="../../../../javax/xml/xpath/XPathExpression.html#evaluate(org.xml.sax.InputSource)">evaluate</A> in interface <A HREF="../../../../javax/xml/xpath/XPathExpression.html">XPathExpression</A><DT><B>Par