Как переделать эту экспертную систему под swi-prolog?

domains 
  s=symbol 
database
  xpositive(s, s)
  xnegative(s, s)
predicates
do_expert_job
do_consulting
ask(s,s)
price_is(s)    
it_is(s)
positive(s,s)
negative(s,s)
remember(s,s,s) 
clear_facts
goal
   do_expert_job. 
clauses
do_expert_job :-
nl,write("* * * * * * * * * * * * * * * * * * * "),
nl,write(" Expert system for the selection of mobile phone."),
nl,write("                                      "),
nl,write("Please, answer the question "),
nl,write("'yes' or 'no'.    "),
nl ,write("* * * * * * * * * * * * * * * * * * * "),
nl,nl,
do_consulting,
readchar(_),
exit.
do_consulting :-
price_is(X),!,nl,
write("The price of your chosen phone  - ",X,"."),nl,
    clear_facts. 
do_consulting :-
  nl,write("You are not satisfied for any of the directory!"),  clear_facts.
ask(X,Y) :-
write(" Question : ",X," it ",Y," ?"),
readln(Reply),
remember(X,Y,Reply).
positive(X,Y) :-
    xpositive(X,Y),!.
positive(X,Y) :-
not(negative(X,Y)),!,ask(X,Y).
negative(X,Y) :-
xnegative(X,Y),!.
remember(X,Y,yes) :-
    asserta(xpositive(X,Y)).
     
remember(X,Y,no) :-
asserta(xnegative(X,Y)),!,fail.
clear_facts :-
retract(xpositive(_,_)),
    fail. 
clear_facts :-
retract(xnegative(_,_)),
fail.
 
  price_is("do 1000grn") :-it_is("Samsung"),
positive(has,"Memory - do 1Gb"),
positive(has,"Camera - 1.3Mpix"),!.
  price_is("1000-1500grn") :-it_is("Samsung"),
positive(has,"Memory - 1-2Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  
  price_is("1500-2000") :-it_is("Samsung"),
positive(has,"Memory - 2-4Gb"),
positive(has,"Camera - vid 2Mpix"),!.
  price_is("vid 2500grn") :-it_is("Samsung"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - vid 2Mpix"),!.
  
price_is("do 1000grn") :-it_is("Nokia"),
positive(has,"Memory - 1-2Gb"),
positive(has,"Camera - 1.3Mpix"),!.
  price_is("1000-1500grn") :-it_is("Nokia"),
positive(has,"Memory - 2-4Gb"),
positive(has,"Camera - 1.3Mpix"),!.
  
  price_is("1500-2500") :-it_is("Nokia"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  price_is("vid 2500grn") :-it_is("Nokia"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - vid 2Mpix"),!.
price_is("do 1000grn") :-it_is("LG"),
positive(has,"Memory - do 1Gb"),
positive(has,"Camera - do 1.3Mpix"),!.
  price_is("1000-1500grn") :-it_is("LG"),
positive(has,"Memory - 2-4Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  
  price_is("1500-2500") :-it_is("LG"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  price_is("vid 2500grn") :-it_is("LG"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - vid 2Mpix"),!.
price_is("do 1000grn") :-it_is("SonyEricsson"),
positive(has,"Memory - do 1Gb"),
positive(has,"Camera - 1.3Mpix"),!.
  price_is("1000-1500grn") :-it_is("SonyEricsson"),
positive(has,"Memory - 1-2Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  
  price_is("1500-2500") :-it_is("SonyEricsson"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - 1.3-2Mpix"),!.
  price_is("vid 2500grn") :-it_is("SonyEricsson"),
positive(has,"Memory - 4-8Gb"),
positive(has,"Camera - vid 2Mpix"),!.
  
  it_is("Samsung") :-
positive(is,"Samsung"),!.
  it_is("LG") :-
positive(is,"LG"),!.
 it_is("Nokia") :-
positive(is,"Nokia"),!.
it_is("SonyEricsson") :-
positive(is,"SonyEricsson"),!.