Functional Dependencies and Disjunctive Existence Constraints in Database Relations with Null Values.

Paolo Atzeni Nicola M. Morfuni Functional Dependencies and Disjunctive Existence Constraints in Database Relations with Null Values. 69-81 1984 conf/icalp/1984 ICALP db/conf/icalp/icalp84.html#AtzeniM84 http://dx.doi.org/10.1007/3-540-13345-3_6