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Logical incompleteness of A-algebra for base deletes

Quote from AntC on October 28, 2019, 11:35 pm
Quote from p c on October 28, 2019, 9:06 pm

Very sorry for expecting some effort on the part of the reader.

Paul I find you patronising, insulting and offensive. I think the moderator would be well within rights to ban you for this answer alone.

As moderator, I will tolerate comments directed at me -- particularly as an emotional reaction to a moderator's comment like my post #21 -- that I will not tolerate being directed at others. Had Paul directed his insult at anyone else, he would be gone now.

I'm the forum administrator and lead developer of Rel. Email me at with the Subject 'TTM Forum'. Download Rel from
Quote from p c on October 28, 2019, 9:32 pm

"What sort of contradiction might base deletion -- say, a bogus tuple in an Inventory base relvar -- raise that would cause a problem?"

It's well-known that a contradiction in a system allows simultaneous true and false answers to the same question.  If the system is a dbms who would want to depend on its answers to queries?  This should have been covered in your courses.

Once again, that is not an answer to the question that was actually asked.

The question was to identify a sort of contradiction that could result from an act of deletion and that would in addition "cause a problem".

I can imagine carrying out a deletion might raise a contradiction with stated integrity rules, but that won't "cause a problem" because the integrity rules are enforced and the deletion will be rejected if such contradiction would arise.

That's just an observation, not an invitation to respond.