3.3.10 Prefix Handling
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Availability::- use_module(library(semweb/rdf_db)).
Source[nondet]rdf_current_prefix(:Alias, ?URI)
Query predefined prefixes and prefixes defined with rdf_register_prefix/2 and local prefixes defined with rdf_prefix/2. If Alias is unbound and one URI is the prefix of another, the longest is returned first. This allows turning a resource into a prefix/local couple using the simple enumeration below. See rdf_global_id/2. 
rdf_current_prefix(Prefix, Expansion),
atom_concat(Expansion, Local, URI),