John Miles Smith Diane C. P. Smith Database Abstractions: Aggregation and Generalization. 105-133 TODS2/P105.PDF 1977 2 ACM Trans. Database Syst. 2 db/journals/tods/tods2.html#SmithS77 http://doi.acm.org/10.1145/320544.320546 db/journals/tods/SmithS77.html persons/Codd71a ... ... journals/cacm/SmithS77