conf/sigmod/79 David W. Shipman The Functional Data Model and the Data Language DAPLEX (Abstract). 59 1979 SIGMOD Conference db/conf/sigmod/sigmod79.html#Shipman79 SIGMOD79/P059.PDF http://doi.acm.org/10.1145/582095.582105 db/conf/sigmod/Shipman79.html