Logical incompleteness of A-algebra for base deletes
Quote from p c on October 28, 2019, 8:37 pm" ... In your latest posts -- i.e., those in this thread -- you haven't even mentioned Tutorial D implementations. ..."
Bingo for the second time! Now i know that besides not understanding, you are not even reading and maybe not even thinking.
A rule I learned to follow many years ago is that in this field, it's a bad idea to tell people whose actions have potentially wide effect how to do things. The result will usually be a disaster, and usually the disaster won't even be recognized. It is best that those people do nothing or if they do, keep it to themselves until they completely understand. Whereas the rarer truly serious people will think for themselves, even when pressured to move quickly. Much less chance of disasters that way.
Histrionics really doesn't belong here or anywhere. If you have a concern with something, please explain it clearly. If you can't -- which is almost certainly the case here -- please keep it to yourself.
"... In other words, what does it mean in real-world terms for it to be the case that "any system that reflects this argument is logically incomplete"?"
It becomes impossible to prove the system has no contradictions.
Quote from p c on October 28, 2019, 8:42 pmQuote from Dave Voorhis on October 28, 2019, 8:30 pmIn other words, what does it mean in real-world terms for it to be the case that "any system that reflects this argument is logically incomplete"?
Good grief. Bingo a third time. You do not understand that incompleteness means results are not provable and probably ignore future uses of relational logic. Welcome to file systems.
Nonsense. Database management systems are ultimately practical tools. If -- and I'm largely guessing here, because you seem unwilling to explain it clearly -- you've found some fundamental flaw with deleting a product tuple from the Inventory relvar because it was entered it in error (say, because the cat walked on the keyboard again) then I'm fine with that fundamental flaw, because:
- Millions, maybe billions or even trillions of tuples/rows are intentionally deleted from databases every day and we haven't had a problem yet; and
- That product tuple needs to be deleted from Inventory no matter what your "logic" says.
It seems the only real problem here is either with your logic and/or your ability to articulate it. There's no problem with "base deletes".
He's got you going again, hasn't he.
The trouble with responding to p_c remarks that make sense is that it's a response, which leads to another and another and another until the descent into gibberish is complete. One of his remarks somewhere (I don't feel like trawling through it all) was about an analogy or equivalence between material implication and set membership. That's simple, obvious, and wrong: it would have to be between material implication and subsetting. But I didn't correct it, because I knew where I would be going if I did.
Resist Geek Answer Syndrome! Put a sock in it! :-)
Quote from p c on October 28, 2019, 8:52 pm"... In other words, what does it mean in real-world terms for it to be the case that "any system that reflects this argument is logically incomplete"?"
It becomes impossible to prove the system has no contradictions.
What sort of contradiction might base deletion -- say, a bogus tuple in an Inventory base relvar -- raise that would cause a problem?
If you mean there might be (automated) proposed optimisations that can't be automatically proven, that can and often does happen with certain kinds of code (including query) optimisers. It's not a problem; if the optimiser can't prove a proposed optimisation, it simply rejects it and either chooses another (assuming it's provable) or it doesn't apply an optimisation.
The result may not achieve some theoretically-possible ideal performance, but proving that the intended operation works (e.g., if we delete a tuple, does the tuple go away?) is technically trivial; it doesn't require proof that some proposed optimisation of the delete isn't theoretically contradictory.
If that makes it a "file system", then so be it. That will be your definition of "file system", but it won't be anyone else's.
Quote from johnwcowan on October 28, 2019, 8:59 pmHe's got you going again, hasn't he.
The trouble with responding to p_c remarks that make sense is that it's a response, which leads to another and another and another until the descent into gibberish is complete. One of his remarks somewhere (I don't feel like trawling through it all) was about an analogy or equivalence between material implication and set membership. That's simple, obvious, and wrong: it would have to be between material implication and subsetting. But I didn't correct it, because I knew where I would be going if I did.
Resist Geek Answer Syndrome! Put a sock in it! :-)
Dammit! There's a big hook in my mouth again!!!
Quote from Dave Voorhis on October 28, 2019, 8:42 pmQuote from p c on October 28, 2019, 8:37 pm" ... In your latest posts -- i.e., those in this thread -- you haven't even mentioned Tutorial D implementations. ..."
Bingo for the second time! Now i know that besides not understanding, you are not even reading and maybe not even thinking.
A rule I learned to follow many years ago is that in this field, it's a bad idea to tell people whose actions have potentially wide effect how to do things. The result will usually be a disaster, and usually the disaster won't even be recognized. It is best that those people do nothing or if they do, keep it to themselves until they completely understand. Whereas the rarer truly serious people will think for themselves, even when pressured to move quickly. Much less chance of disasters that way.
Histrionics really doesn't belong here or anywhere. If you have a concern with something, please explain it clearly. If you can't -- which is almost certainly the case here -- please keep it to yourself.
Very sorry for expecting some effort on the part of the reader. Try the two one-liner arguments I just gave. All you need to do is type them in and press a button. For a shallow understanding you won't even need to read a truth table. Somebody with the university logic education mentioned earlier should understand the symbolic arguments almost immediately.
"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.
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.
(Sorry, @johnwcowan)
An update isn't a query. Furthermore, a typical DBMS doesn't implement Appendix A algebra or a logic engine (at least, not as such). A typical implementation per TTM will implement relational algebra operators -- whose semantics, as we know, are straightforward -- using Appendix A only as reference material to inform the developer's understanding of relational algebra semantics. (I am aware that it is possible to directly implement Appendix A and make that be the query language, but that's something else. It's certainly not Tutorial D.) Thus, even if there is some logical contradiction in some definition of RA operator semantics -- and I am by no means convinced there is (in other words, I'm quite certain there isn't) -- the Tutorial D operators are intuitive and obvious and straightforward to implement and prove correct in and of themselves, so it's a non-issue.
As I mentioned before, where it could conceivably be a problem is in a query optimiser -- assuming it is based on Appendix A definitions -- so that an error in definitions could lead to a false equivalence of some proposed optimisation and its non-optimal equivalent. I.e., if it turns out that some optimisation Y of code X that is assumed to be equivalent to X turns out to be not equivalent to X.
But that's rather far outside of the realm of possibility. The optimisations for base relvar deletion are trivial, such that I can't think of any contradiction that would be raised even by an optimiser. Furthermore, such an Appendix-A-logic-engine-based query optimiser is unlikely; it's more likely to use well-known code optimisations for imperative code, and relational operator expression equivalences for RA expressions, same as typical SQL query optimisers and the like.
Anyway, it certainly isn't a problem for Rel. The minimal query optimisation (very minimal) that is done is mostly on speeding up JOINs. There's nothing in Appendix A, right or wrong, related to base relvar deletion or anything else that would have the slightest impact.
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.
I expect first "some effort" on the part of the writer. Everybody here at some time or other has tried to suggest politely, and then not so politely how you might improve your posts to communicate more clearly -- that is, supposing you have something to communicate. (I think nobody has found more than a few scraps of sense, certainly not enough to count as a communication.)
Specifically on this thread, I suggested that if you're giving predicate logic, use predicate logic symbols; if you're giving set theory, use set theory symbols; state which formulas are using which symbolism; if you're giving references, put unambiguous links or citations. This is the most basic "effort". You've mixed set theory and predicate calculus in the same sentence (at least that's my guess what they were) and using the - in both, in places monadic/prefix in other places dyadic/infix.
Try the two one-liner arguments I just gave. All you need to do is type them in and press a button. For a shallow understanding you won't even need to read a truth table. Somebody with the university logic education mentioned earlier should understand the symbolic arguments almost immediately.
I have a "university logic education" thank you (specifically a BA Hons in Philosophy, specialising in symbolic logic, epistemology, logic of scientific discovery, logical positivism). Your writings read as the ravings of a deranged mind. I see nothing logical. I see scraps of logic symbolism mixed up with woo-hoo.
Your writings exhibit all the tendencies of what's called a 'private language'. The terms (although they appear to be English words) are used not in familiar senses but in some internal (to you) mental recitation. Accusing someone of "file system" mentality seems to be some sort of personal mantra to you; those words have come adrift from their semantic moorings.
Then you don't need to talk to yourself in any forum atall. Find out what is your email address, and send your messages to that.