SWI-Prolog -- rdf_current

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_current_literal(-Literal)

True when Literal is a currently known literal. Enumerates each unique literal exactly once. Note that it is possible that the literal only appears in already deleted triples. Deleted triples may be locked due to active queries, transactions or snapshots or may not yet be reclaimed by the garbage collector.