ion">
   XQuery 1.0 and XPath 2.0 Data Model, xdt:yearMonthDuration</a>.</p>
 
 <p>The XML Schema specification states that values can be of an arbitrary size.
 Implementations may chose not to or be incapable of supporting arbitrarily large and/or small values.
 An <CODE>UnsupportedOperationException</CODE> will be thrown with a message indicating implementation limits
 if implementation capacities are exceeded.</p>
 
 <p>A <code>null</code> value indicates that field is not set.</p><DD><DL>
<DT><B>Paramet