Hello,
I am using rdf_meta to be able to use abbreviated notation for RDF resources. For example, the directive :
rdf_meta
my_pred(r).
allows me to call my_pred(dpe:p1). rather than the fully quantified URI.
However, when my_pred is defined over multiple files (using dynamic/2) this no longer seems to work as illustrated by the following example that is composed of two modules (base and ext), and a scenario from the SWI. command line
base.pl:
:- module(base,[t_ok/1,t_nok/1]).
:- dynamic([t_ok/1,t_nok/1],[multifile(true)]).
:- use_module(library(semweb/rdf11)).
:- rdf_meta
t_ok(r),
t_nok(r). % note t_nok/1 is defined in ext.pl (but it is part of the "base" module)
t_ok(dc:a). % dc:a is an abbreviated. URI
ext.pl:
:- module(ext,[]).
:- reexport(base).
:- use_module(library(semweb/rdf11)).
:- dynamic([base:t_nok/1],[multifile(true)]).
base:t_nok(dc:b). % dc:b is an abbreviated. URI
the scenario :
% swipl
Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.25-4-ge2c781d07)
?- [ext]. % this also loads base
true.
?- use_module(library(semweb/rdf11)).
true.
?- rdf_assert(dc:a,p,o),rdf_assert(dc:b,p,o). % populate the repository with two triples
true.
?- t_ok(S),rdf_subject(S). % all is fine for t_ok/1 that is defined in base.pl
S = 'http://purl.org/dc/elements/1.1/a'.
?- t_nok(S),rdf_subject(S). % however t_nok/1 that is defined in ext.pl, but part of
% base.pl, thinks dc:b is a compound term iso an abbreviated URI
ERROR: Type error: `atom' expected, found `dc:b' (a compound)
ERROR: In:
ERROR: [12] rdf_db:rdf_resource(dc:b)
ERROR: [11] rdf_db:rdf_subject(dc:b) at /usr/local/lib/swipl/library/semweb/rdf_db.pl:522
ERROR: [9] <user>
...
Is there a way to convince rdf_meta to work with predicates defined over multiple modules, or am I pushing my luck here? Many thanks for any hints you may have
Joost