Prolog - Merging Symbols (or Terms?)

(Pardon if my terminology is wrong... I'm new to Prolog.)

Suppose you have a series of symbols appearing in some unknown number of predicates.

f1(a, b, c, d).
f2(b, b, c).
...
fn(b, d, e).

Later--at runtime--you realize that terms a and b are the same, and you wish to merge them or replace one of them with the other. In other words, I would like to either:

• Make a = b
• Replace all instances of a with b
• Replace a and b with a new symbol (made through gensym/2)
• ...or anything else that accomplishes this

... where I do not know wh开发者_Go百科ich predicates use these terms.

Atoms that start with upper case letters are variables. The first step then is to use A and B. If at some point you decide two variables are actually equal, you just say it A = B. The process of stating logically that one thing = another is "unification".

e.g.

veryDifferentOrTheSame(A,B) :- veryDifferent(A,B).
veryDifferentOrTheSame(A,B) :- A = B.

Of course, unification won't always work. a(X) = b(X) will fail.

This all implies that when the code was written, you knew that you weren't sure A=B.

You can also dynamically assert clauses at runtime. Declaring a clause as dynamic and using assera or assertz.

But if you state:

iOwn(goldfish).
iOwnFish :- iOwn(fish).

and then want to make that work by saying "in my universe fish = goldfish", then you're in strange territory.