SPARQL allows custom property functions to add functionality to the triple matching process. Property functions can be registered or dynamically loaded.
See also the free text search page.
See also the FILTER functions FILTER functions library.
Applications can also provide their own property functions.
The prefix apf is <http://jena.apache.org/ARQ/property#>. (The old prefix of <http://jena.hpl.hp.com/ARQ/property#> continues to work. Applications are encouraged to switch.)
Direct loading using a URI prefix of <java:org.apache.jena.sparql.pfunction.library.> (note the final dot) also works.
The prefix list: is http://jena.apache.org/ARQ/list#.