Re: MV Keys


"vc" <boston103@xxxxxxxxxxx> wrote in message
news:1141824160.347616.85480@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Brian Selzer wrote:
[...]
"x is 2" is a sentence; "y is 3" is a sentence.
"x is 2 and y is 3" is also a sentence.

You are confused. "x is 2" is not a sentence in the contex of FOL.
It's a predicate with a free variable which will become a sentence if
you substitute a constant for x.


It isn't? So, what you're saying is the statement, "Joe is 30 years old" is
not a statement in FOL? As I said, I'm not a logician, so I don't speak
their jargon. I guess I don't speak their language either.

If E(x in X)(x = 2) and E(y in Y)(y = 3) are predicates, would a predicate
with an variable that belongs to the cartesian coordinate domain be a
statement in second order logic? I'm not being facetious, I'd really like
to know.


Thus a tuple in a relation R{A, B, C} is the
set of propositions {A has value 3, B has value 7, C has value 2}. The
tuple itself also has a truth value, "A has value 3 and B has value 7 and
C
has value 2." which is a proposition in conjunctive normal form.

You are confused even more. A relation is simply an interpretation of
some predicate (which is an element of a FOL language). A tuple is an
element of such relation.

So, you're saying that an element of a relation doesn't have a truth value?


.

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