SWI-Prolog -- rdf

Documentation
- Reference manual
- Packages
  - SWI-Prolog Semantic Web Library 3.0
    - Two RDF APIs
      - library(semweb/rdf_db): The RDF database
        
        Enumerating objects
        
        rdf_subject/1
        
        rdf_resource/1
        
        rdf_current_predicate/1
        
        rdf_current_literal/1
        
        rdf_graph/1
        
        rdf_current_ns/2

Availability::- use_module(library(semweb/rdf_db)).

[nondet]rdf_resource(?Resource)

True when Resource is a resource used as a subject or object in a triple.

This predicate is primarily intended as a way to process all resources without processing resources twice. The user must be aware that some of the returned resources may not appear in any visible triple.