The man who wasn't there: The problem of partially missing data

Existing commercial database management systems offer little or no functionality to handle the complexity of geoscience data-and other environmental science data-particularly in respect of missing and partially missing (incomplete or imprecise) data items. The emphasis of both the relational theorists (Codd, Date, and others) and the developers of database systems is on commercial applications where only rudimentary treatment of missing data is required, in the form of NULLs, and even these are not handled properly by the SQL language.