Query optimization and processing in federated database systems
Ee‐Peng Lim, Jaideep Srivastava · 1993
this paper, we have selected a minimal set of core operations that includes the set of relational operations, i.e. foe,ß,1,\\Gamma,[g, as well as three other operators which are useful in specifying the federated views. These are 2-way Outerjoin Operator (