gistfile1.xml

Option 1: no form:

<b:modal>
 <f:facet name="header">
  ...
 </f:facet>
 some body content here
 <f:facet name="footer">
  ...
 </f:facet>
</b:modal>

with a form:

<b:modal>
 <h:form>
  <b:body>
   <f:facet name="header">
    ...
   </f:facet>
   some body content here
   <f:facet name="footer">
    ...
   </f:facet>
  </b:body>
 </h:form>
</b:modal>