Validation not working in sun idm(oracle waveset) form

Question

I have put this validation code in my form.
<Field>
<Validation>
<cond>
<gt><i>6</i>
<i>5</i>
</gt>
<s>zip codes must be five digits long</s>
<s>zip codes must be five digits long</s>
</cond>
</Validation>
</Field>
But on submit of form this validation code is not getting called.
It is given in sun idm docs that validation message appears in red at top of the form.
But it is not getting displayed in my case.
How to get message to display on form.
OR
how to get any message displayed on form present inside validation tag.

Answer 1

As requested
        <Field name=':variables.xxxWorkstationID'>
          <Display class='Text'>
            <Property name='title' value='Workstation Name'/>
            <Property name='size' value='25'/>
            <Property name='maxLength' value='25'/>
            <Property name='required' value='true'/>
            <Property name='help' value='Please provide the workstation name'/>
          </Display>
          <Derivation>
            enter your form code here
          </Derivation>
          <Validation>
            <cond>
              <not>
                <eq>
                  <invoke name='callResourceMethod' class='com.waveset.ui.FormUtil'>
                    <ref>:display.session</ref>
                    <ref>:variables.xxxResName</ref>
                    <s>validateWorkstation</s>
                    <map>
                      <s>Workstation</s>
                      <ref>:variables.xxxWorkstationID</ref>
                    </map>
                  </invoke>
                  <i>0</i>
                </eq>
              </not>
              <s>Error. The Workstation Name is not valid. Please re-enter a valid name.</s>
            </cond>
          </Validation>
</Field>