On 7/29/13 3:59 AM, Jerven Bolleman wrote:
Dear Virtuoso devs,What is the ASSUME variable that you added in 6.1.7 ? http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/ I can't find any reference to this in the SPARQL 1.1 query standard. Is this a virtuoso specific extension? Regards, Jerven
Neither can I :-) This is clearly a typo in the release notes. Basically, this is a Virtuoso specific query optimizer hint:It gives a hint to the optimizer that the expression X is always true and the optimizer should work as such where you have ASSUME, while not triggering any SQL code generation for checking whether X is true (since it is ASSUMED to be true). Thus, in the example below, it is ASSUMED that ?id is an IRI, so there's not need for any further type checking further down in the query-optimizer's processing workflow.
Usage Example:
SELECT * WHERE { ?s1
<id> ?id ;
geo:lat ?lat ;
geo:long ?long .
GRAPH ?rdf_view_g
{ ?s2
<id> ?id ;
rdfs:label ?label
} .
ASSUME (isIRI (?id)) }
--
Regards,
Kingsley Idehen
Founder & CEO
OpenLink Software
Company Web: http://www.openlinksw.com
Personal Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter/Identi.ca handle: @kidehen
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LinkedIn Profile: http://www.linkedin.com/in/kidehen
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