Prologue for conjunctive normal form
I have this code that I need to translate into CNF (this is exam preparation, so no homework!):
p,q
r :- q
false :- p , s
s :- t
t
Here's what I did:
p ^ q ^ (r V ~q) ^ (~p V ~s) ^ (s V ~t) ^ t
= r
Am I thinking correctly?
There is another question here:
You want to query the database using r. What condition should you add to your database?
I don't understand this at all. After simplifying the database, basically r. r is true, isn't it?
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The question "Do you want to query the database with r. What sentence should you add to your database?" refers to the so-called evidence of refutation. The proof of refutation does not prove:
Database |- Query
Instead of one proof:
Database, ~Query |- f
In classical logic, two are the same. So in your example, you will need to show that p ^ q ^ (r V ~ q) ^ (~ p V ~ s) ^ (s V ~ t) ^ t ^ ~ r leads to a contradiction.
Bye
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