Construct clause step by step - prolog

Question

I would like to construct a clause after a series of steps. For instance, if i verify a condition then i assert a part of a clause. If "the pen is red" i obtain:
color(pen, red)
if "the pen is on the table":
on(pen, table)
if "the table is blue":
color(table, blue)
At the end I have to get:
color(pen, red), on(pen, table), color(table,blue).
I would like to insert the final clause in an external file. How can I do?
EDIT:
I insert a text similar to the above and deduct these separate predicate:
first color(pen,red), second on(pen,table), third color(table,blue)
I would like to obtain a clause that is :
text(t1):- color(pen, red), on(pen, table), color(table,blue).
and this clause must be inserted in a file.
INPUT: single predicate.
OUTPUT: one clause with all predicates.

Answer 1

I'd attack the problem with DCGs.
sentence(S) --> color_statement(S) ; on_statement(S).
det --> [a].
det --> [the].
color_statement(color(Noun, Color)) --> det, [Noun], [is], color(Color).
color(Color) --> [Color], { color(Color) }.
color(red). color(blue).
on_statement(on(Noun, Place)) --> det, [Noun], [is,on], det, [Place].
This is assuming you have some kind of tokenization in place, but for demo purposes, you'll find this "works":
?- phrase(sentence(S), [the,pen,is,on,the,bookshelf]).
S = on(pen, bookshelf).
You will no doubt need to extend these rules for your purposes. You can find tokenization stuff by searching, and only you know exactly the kinds of nouns and modifiers you want to support, so this is really just a sketch of how this could proceed.
From here you're going to create another rule to handle multiple statements.
clause([]) --> [].
clause([S|Rest]) --> sentence(S), ['.'], clause(Rest).
Testing it works like so:
?- phrase(clause(S), [the,pen,is,on,the,bookshelf,'.',the,pen,is,red,'.']).
S = [on(pen, bookshelf), color(pen, red)]
So these are the clauses you want. Now you just need a predicate to bring them together.
list_and([X,Y], (X,Y)).
list_and([X|Xs], (X,Rest)) :- list_and(Xs, Rest).
clause_for(Name, Tokens, Predicate) :-
phrase(clause(Parts), Tokens),
list_and(Parts, AndSequence),
Predicate = (Name :- AndSequence).
This does basically what you want, but you need to furnish a name for your predicate:
?- clause_for(bob, [the,pen,is,on,the,bookshelf,'.',the,pen,is,red,'.'], P).
P = (bob:-on(pen, bookshelf), color(pen, red))
Hope this helps!