Unary conditional problem

[Diran Ayandele]

Hey Guys!
   Is there some simple reason I get this error:
Caused by: org.xml.sax.SAXParseException: The content of element type 
"isEmpty" must match 
"(include|iterate|isParameterPresent|isNotParameterPresent|isEmpty|isNotEmpty|isNotNull|
isNull|isNotEqual|isEqual|isGreaterThan|isGreaterEqual|isLessThan|isLessEqual|isProperty
Available|isNotPropertyAvailable)".
Out of this sql:

   <insert id="insertMetricDocument" parameterClass="MetricDocument">
       <isEmpty property="documentId">
           <selectKey resultClass="string" keyProperty="documentId">
               select SC_METRIC_DOCUMENTS_ID.NextVal from dual
           </selectKey>
       </isEmpty>
       insert into SC_METRIC_DOCUMENTS (
            METRIC_ID,
            DOCUMENT_ID,
            VERSION,
            DOCUMENT_NAME,
            DESCRIPTION,
            FILE_EXTENSION,
            DOCUMENT,
            UPDATE_DATE,
            UPDATED_BY)
       values (
           #metricId#,
           #documentId:NUMERIC#,
           #version#,
           #documentName:VARCHAR#,
           #description:VARCHAR#,
           #fileExtension:VARCHAR#,
           #document#,
           sysdate,
           #updatedBy.employeeNumber#
           )
   </insert>

Thanks!
Diran