Re: [LIU Comp Sci] Need tutoring on Relational Calculus

On 12/21/2014 09:37 PM, compdb_at_hotmail.com wrote:
> (∀ t)(F) doesn't say anything unless it has no free variables.

what does that mean? What is no free variable?

A variable is a storage unit that can take the value of data that can satisfy a condition. This is what the point is , right?

A variable by itself has no defining characteristic. Until we assign it a domain, we have no idea what values might make satisfy a variable.

So we have two things, essentially. We have the character of variable according to its generalized domain which is declarative.

A is a variable that is Real Numbers
A is a variable that is Complex Numbers
A is a variable that is socks in a socks draw.

Then we can a sub domain which is set according to rules of induced reason.

A = X^2 + 3
where A is Real Numbers

Now I have 2 domains to define A.

None of this looks like this syntax:
(∀ t)(F)

So I'm having trouble understanding the term Free in this context, regardless how prosaic that might be. Received on Mon Dec 22 2014 - 08:56:44 CET