More specifically, this invention relates to a query transformation technique to achieve more efficient query processing of systems with {HEAD ~ varying query capabilities} within {TAIL ~ a federated system} 
More specifically , this invention relates to a query transformation technique to achieve more efficient query processing of systems with { HEAD ~ varying query capabilities } within { TAIL ~ a federated system }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL