I want to load rdf url from this rule:
getActorFilms(Actor_Name,Films):-
my_replace(Actor_Name, ' ', '_', Correct_Syntax_Of_Actor_Name),
string_concat('http://dbpedia.org/data/',Correct_Syntax_Of_Actor_Name, URL_TO_LOAD),
string_concat(URL_TO_LOAD,'.rdf',RDF_URL),
rdf_load(RDF_URL),
rdf(Films, 'http://dbpedia.org/ontology/starring', Object)
.
when the input is e.g. for an example 'Hugh Jackman'
it tells the error:
ERROR: [Thread pdt_console_client_0_Default Process] source_sink `http://dbpedia.org/data/Hugh_Jackman.rdf' does not exist
I'm really concerned about the ` character between http and source_sink
I think it should be '
although the url is correct, so what to do with that error?
You should pass an atom to rdf_load, not a string. This behavior (the misleading error message, not accepting a string) is probably a bug.
This works for me:
?- use_module(library('semweb/rdf_db')).
true.
?- use_module(library('semweb/rdf_http_plugin')).
true.
?- rdf_load('http://dbpedia.org/data/Hugh_Jackman.rdf').
% Parsed "http://dbpedia.org/data/Hugh_Jackman.rdf" in 0.02 sec; 371 triples
true.
?- string_to_atom(S, 'http://dbpedia.org/data/Hugh_Jackman.rdf'), rdf_load(S).
ERROR: source_sink `http://dbpedia.org/data/Hugh_Jackman.rdf' does not exist
I hope this solves your problem.
Related
I am trying to compile and query this code:
got('no').
inMap(X,Y):- print("From inMap").
mask(1,3).
doctor(2,1).
verify(X,Y):-
(inMap(X,Y), ((\+(got('mask'); got('vaccine')),farCovid(X,Y)); True),
(print(X), print(Y); True),
(doctor(X,Y), print(X), print(Y); True)).
When my query is:
?- verify(2,1).
It returns:
"From inMap""From farCovid"2121
true .
But when my query is:
?- verify(1,1).
It returns:
"From inMap""From farCovid"11
ERROR: Arguments are not sufficiently instantiated
ERROR: In:
ERROR: [10] verify(1,1)
ERROR: [9] <user>
Can somebody explain to me what is wrong here please, wasn't it supposed to pass in (1,1) in the second query to doctor(X,Y) and return false?
Thanks in advance!
I am doing exercise from the following link
Here is knowledge base:
house_elf(dobby).
witch(hermione).
witch(’McGonagall’).
witch(rita_skeeter).
magic(X):- house_elf(X).
magic(X):- wizard(X).
magic(X):- witch(X).
I am expecting the following query to return true:
?- magic(’McGonagall’).
However, my SWI-Prolog (AMD64, Multi-threaded, version 7.6.4) on Windows 7 returns the following:
ERROR: Stream user_input:450:4 Syntax error: Unexpected end of clause
?- magic('McGonagall').
ERROR: Undefined procedure: wizard/1
ERROR: In:
ERROR: [9] wizard('McGonagall')
ERROR: [8] magic('McGonagall') at c:/users/some_user/google drive/projects/nlp/prolog/code/ex2_2.pl:6
ERROR: [7] <user>
Exception: (9) wizard('McGonagall') ? creep
Exception: (8) magic('McGonagall') ? creep
?-
Why does it fail?
In the magic/1 predicate, you call wizard/1, which is not defined:
magic(X):- house_elf(X).
magic(X):- wizard(X).
magic(X):- witch(X).
The result is that Prolog errors, since it calls a predicate that is nowhere defined.
You can for example define a wizard/1 predicate that always fails:
% a world without wizards (if you do not specify extra wizards)
wizard(_) :- fail.
or populate your "world" with wizards, like:
wizard(dumbledore).
wizard(remus_lupin).
%% ...
I am learning Prolog and .(a,[]) == [a]. should return true in SWI-Prolog, but it gives me an error saying
ERROR: Type error: `dict' expected, found `a' (an atom)
ERROR: In:
ERROR: [11] throw(error(type_error(dict,a),_4020))
ERROR: [10] '$type_error'(dict,a) at /Applications/SWI-
Prolog.app/Contents/swipl/boot/init.pl:3369
ERROR: [9] '$dicts':'.'(a,[],_4086) at /Applications/SWI-
Prolog.app/Contents/swipl/boot/dicts.pl:46
ERROR: [8] '<meta-call>'(user:(...,...)) <foreign>
ERROR: [7] <user>
Anyone knows how to fix this?
Start the SWI Prolog executable with the --traditional command line option (comment due to user:false).
Then it works:
1 ?- .(a,[]) == [a].
true.
2 ?- current_prolog_flag( traditional, X).
X = true.
3 ?- set_prolog_flag( traditional, false).
ERROR: set_prolog_flag/2: No permission to modify flag `traditional'
4 ?-
This is mentioned in the documentation here (see "traditional", near the bottom of the page).
As can be seen, attempting to change it from within the running SWI session, fails.
I am using gprolog allong with gplc and I get fatal error: redefining built-in predicate member/2 when I try to compile the following code. I also get uncaught exception: error(existence_error(procedure,member/0),member/0) when I try to consult the same code.
Code:
member(X,[X|T]).
member(X,[H|T]) :- member(X,T).
The query I give:
| ?- member(X,[a,b,c,d,e]).
X = a ? ;
uncaught exception: error(existence_error(procedure,member/0),member/0)
So I'm trying to test my the predicate reduce/4 defined as following:
:- op(20,xfy,?=).
reduce(R,X ?=Y,P,Q) :-
R=rename,
regle(X ?=Y,R),
length(P,N),
trouve(Y,P,N,M),
remove(N,M,P,Q).
but i keep getting this error:
?- reduce(rename,X ?= Y,[?=(X,Y),?=(f(a),g(Z)),?=(X,a)],Q].
ERROR: Syntax error: Illegal start of term
ERROR: reduce(rename,X ?= Y,[?=(X,Y),?=(f(a),g(Z)),?=(X,a)],
ERROR: ** here **
ERROR: Q] .
I'm new to Prolog so maybe it is something stupid.
You use ] instead of ) to close the bracket of reduce
reduce(rename,X ?= Y,[?=(X,Y),?=(f(a),g(Z)),?=(X,a)],Q].
% ^open ^close
You can fix this with:
?- reduce(rename,X ?= Y,[?=(X,Y),?=(f(a),g(Z)),?=(X,a)],Q).
I cannot validate if this solves your problem, because you did not provide a definition for regle/2, etc. But the fact that I get a semantic error, seems to solve the syntax error nevertheless.