Craig,

>>Yes based on the assumption that either CODD and DATE regard the existance of deleted records. Remember that with the introduction of the RM xBase did not exist yet, neither did the existance of delete records.

>Wrong. My copy of Date is the fourth edition, published in 1986. dBase existed then.

Please craig.. read carefully, I said: that with the introduction of the RM (1970.. 1971) xBase did not exist yet.

>>CODD describes a theory (the RM); the theory certainly exists. Date describes both the RM and (R)DBMSs features. Both the RM theory and the (R)DBMSs certainly exists.
>
>Both exist in theory, but no product exists that adheres precisely to what they described.

Right, and there are good reason for it. It is simply not practical.


Walter,