></CODE></B></DD>
<DD>Override to determine whether according to the validator, the cached 
 module script needs revalidation. A validator can carry expiry 
 information. If the cached representation is not expired, it doesn'
 t need revalidation, otherwise it does. When no cache revalidation is
 required, the external resource will not be contacted at all, so some 
 level of expiry (staleness tolerance) can greatly enhance performance. 
 The default implementation always returns true so it will always requ