HI Jamey,
Does Virtuoso provide some supported way to write one's own custom
SPARQL extension functions (http://www.w3.org/TR/rdf-sparql-query/#extensionFunctions
)?
Yes, there are actually two options:
Firstly, you can create a stored procedure in Virtuoso PL and call it
using the sql: prefix:
SELECT * where { ?s ?p `sql:testfunc(?o)` }
See: http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfsqlfromsparql
Secondly you can make a build in function which is basically a C
function that can be called from both SQL and SPARQL as in the
following examples, using the bif: prefix:
In this example we use the CONTAINS function to do a freetext search
on all ?o that contain words starting with Timo.
SELECT * FROM <http://www.w3.org/people#> WHERE { ?s ?p ?o . ?o
bif:contains '"Timo*"'}
See:
http://docs.openlinksw.com/virtuoso/sparqlextensions.html#rdfsparqlrulefulltext
You can basically use relevant functions from the Virtuoso Functions
Guide inside your SPARQL query.
See: http://docs.openlinksw.com/virtuoso/functions.html
Best regards,
Patrick
