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Availability::- use_module(library(semweb/rdf11)).
[nondet]rdf_subject(?S)
True when S is a currently known subject, i.e. it appears in the subject position of some visible triple. The predicate is semidet if S is ground.
Availability::- use_module(library(semweb/rdf_db)).
Source[nondet]rdf_subject(?Resource)
True if Resource appears as a subject. This query respects the visibility rules implied by the logical update view.
See also
rdf_resource/1.