I want to write a program in Prolog where a menu is given to the users. They choose to either add data, see existing data based on surname or age, or/and delete data based on surname or age. I don't know how to delete an entry based on age or surname. Here is what I've written. Can anyone tell me what I do wrong? Thank you.
:- use_module(library(semweb/rdf_db)).
:- use_module(library(semweb/rdf_http_plugin)).
:- use_module(library(semweb/turtle)).
:- dynamic id/1.
id(1).
run :- nl,
write('Option 1: Load new path'),nl,
write('Option 2: Create new user'),nl,
write('Option 3: Display data based on Surname'),nl,
write('Option 4: Display data based on Age'),nl,
write('Option 5: Delete data based on Surname'),nl,
write('Option 6: Delete data based on Age'),nl,
write('Option 7: Exit'),nl, %It saves the program before exiting
write('Option(1-7): '), read(X), nl,
( shouldExit(X)
; (option(X), run)
; (nl, write('Invalid option.'), nl, run)
).
shouldExit(7) :- save.
option(1) :- write('Give path for rdf file'), read(Path), doOpen(Path).
option(2) :- doRead.
option(3) :- write('Surname: '), read(Surname), findS(Surname).
option(4) :- write('Age: '), read(Age), findA(Age).
option(5) :- write('Surname: '), read(Surname), delS(Surname).
option(6) :- write('Age: '), read(Age), delA(Age).
/*Enter new user*/
doRead :- rdf_register_prefix(foaf,'http://xmlns.com/foaf/0.1/'),
write('Surname:'), read(Surname),
write('First Name:'), read(FirstName),
write('Age:'), read(Age),
id(N),
New is N+1,
retract(id(N)),
asserta(id(New)),
atom_concat('foaf:person', N, Person),
rdf_assert(Person, rdf:type, foaf:'Person'),
rdf_assert(Person, foaf:surname, literal(Surname)),
rdf_assert(Person, foaf:firstName, literal(FirstName)),
rdf_assert(Person, foaf:age, literal(Age)).
/*Display data based on Surname*/
findS(Surname) :- rdf(X, foaf:surname, literal(Surname)),
rdf(X, foaf:firstName, literal(FirstName)),
rdf(X, foaf:age, literal(Age)),
write('Found '), write(FirstName), write(' '),
write(Surname), write(', '), write(Age), nl, fail.
/*Display data based on Age*/
findA(Age) :- rdf(X, foaf:surname, literal(Surname)),
rdf(X, foaf:firstName, literal(FirstName)),
rdf(X, foaf:age, literal(Age)),
write('Found '), write(FirstName), write(' '),
write(Surname), write(', '), write(Age), nl, fail.
/*Loads the file from the path the user asks ''*/
doOpen(Path) :- rdf_load(Path).
/*Saves the changes before exiting*/
save :- rdf_save(Path, [foaf]).
/*Deletes user based on their surname*/
/*delS(Surname) :- .*/
/*Deletes user based on their age*/
delA(Age) :- rdf(X, foaf:surname, literal(Surname)),
rdf(X, foaf:firstName, literal(FirstName)),
rdf(X, foaf:age, literal(Age)),
retract(rdf(Surname, FirstName, Age)).
I don't know it, so this is a guess, but you are using:
retract(rdf(Surname, FirstName, Age)).
and that is Prolog retract/1, I think you need rdf_retractall instead.