/code> of type <code>xdt:yearMonthDuration</code> using the specified
 <code>year</code> and <code>month</code> as defined in
 <a href="http://www.w3.org/TR/xpath-datamodel#dt-yearMonthyDuration">
   XQuery 1.0 and XPath 2.0 Data Model, xdt:yearMonthDuration</a>.</p>
 
 <p>A <A HREF="../../../javax/xml/datatype/DatatypeConstants.html#FIELD_UNDEFINED"><CODE>DatatypeConstants.FIELD_UNDEFINED</CODE></A> value indicates that field is not set.</p><DD><DL>
<DT><B>Parameters:</B><DD><CODE>isPositive</CODE> - Set t