Re: adjective noun first order logic

On Dec 6, 9:07 pm, David C. Ullrich <ullr...@xxxxxxxxxxxxxxxx> wrote:
On Wed, 5 Dec 2007 23:24:57 -0800 (PST), Keenlearner

<yin...@xxxxxxxxx> wrote:
Thanks for the reply, actually I was thinking to write "John is an old
man", but I thought that will give raise of existential quantifier,
because I want it to be simpler. Why is there not existential
quantifier for "John is an old man" ? Thank you.

Because "John" is a _constant_, not a _variable_.

At least I'm assuming from the context that "John" is
supposed to be a constant instead of a variable - you
didn't mean to say "there exists an old man", did you?
You meant to say something about John specifically,
right?

Find a book on logic - the way constants work is
different from the way variables work.



On Dec 6, 5:23 am, David Ullrich <ullr...@xxxxxxxxxxxxxxxx> wrote:
Keenlearner wrote:
I am doing natural language processing research, I was wondering which
is the correct way of representing "old man John" in first order
predicate calculus, later on this logic will be converted into Prolog
clauses.

old(john) ^ man(john)

old(john) => man(john)

man(john) => old(john)

if you think one is wrong or right please tell me why ?! Thank you
very very much.

None of those is a correct "representation" of "old man John",
because they are all (representations of) _assertions_, and
"old man John" is not an assertion.

If ^ means "and" then "old(John) ^ man(John)" is a correct
representation of the _assertion_ "John is an old man".
That's not the same thing.

************************

David C. Ullrich

Thank you, I love you all so much...hehe.I got it now.

Anyway, I found a Prolog natural language program from
www.mtome.com/Publications/PNLA/prolog-digital.pdf
I have extend a little bit on it, for sentence input of "Every
student is on a table" it will generate the FOL

Let's say
A "Universal quantifier"
E "Existential quantifier"
and "conjunction"
or "disjunction"
=> "implication"

A x (student(x) => E y ( table(y) and on( x, y)))

is this correct ?


Whether it's correct or not, as you can see there is two conclusions
or literals.
Prolog is somehow from Horn Clauses, they can have at most one
positive literals.
In this case, how can I convert the FOL that have two positive
literals into Prolog ? Thank you.
.

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