You should enter woman(mia). into a file to assert it as a fact. If you write it into the interpreter, it's taken as a query, not a fact.
From the SWI Prolog FAQ:
Terms that you enter at the toplevel are processes as queries, while
terms that appear in a file that is loaded into Prolog is processed as
a set of rules and facts. If a text reads as below, this is a rule.
carnivore(X) :- animal(X), eats_meat(X).
Trying to enter this at the toplevel results in the error below. Why?
Because a rule is a term :-(Head, Body), and because the toplevel
interprets terms as queries. There is no predicate with the name :-
and two arguments.
?- carnivore(X) :- animal(X), eats_meat(X). ERROR: Undefined
procedure: (:-)/2 ERROR: Rules must be loaded from a file ERROR:
See FAQ at http://www.swi-prolog.org/FAQ/ToplevelMode.txt
Isn't this stupid? Well, no. Suppose we have a term
eats_meat(rataplan). If this appears in a file, it states the fact
that rataplan eats meat. If it appears at the toplevel, it asks Prolog
to try proving whether rataplan eats meat.
If a text reads
:- use_module(library(clpfd)).
This is a directive. Directives are similar to queries, but instead of
asking the toplevel to do something, they ask the compiler to do
something. Like rules and facts, such terms belong in files.
Instead of writing to a file you can also use assert in the toplevel (as explained later in the FAQ as well).
