Generating values for empty attributes

Question

I am trying to fill the empty spaces generated by the use of Optional in the SPARQL query language. Are there any ways that I can achieve this?

The use of !bound on the optional variable generates true or false, but I want to fill the cells with my own values such as "?" or "unknown".

Select ?a ?b ?c Where ?a1 rdfs:type hvs:whi; rdfs:label ?a ?a2 rdfs:type hvs:whi; rdfs:label ?a Optional ?s1 rdf:type hvs:whi; rdfs:label ?b . ?m hvs:wmm ?a; hvs:into ?s1; hvs:will ?c . Filer (?c =1 ll ?c = 2 ll (!bound (?c) = 'unknown') Issue: the resultset has some ?c without values (empty cells). I want to replace these cells with 'unknown'. Sorry that i cound not follow strickly the syntax of sparql with respect to curves. I am using my phone to type. Regards — honour nwagwu, Nov 01 '13 at 12:04

w5m · Answer 1 · 2013-11-01T14:46:20.417

8

Perhaps you could use one of the following constructs...

COALESCE(?c, "unknown")

or

IF(bound(?c), ?c, "unknown")

edited Nov 01 '13 at 14:46

answered Nov 01 '13 at 14:25

w5m

[This answer](http://stackoverflow.com/a/16080026/1281433) by AndyS gives some more examples. – Joshua Taylor Nov 01 '13 at 21:25
Thanks so much. I achieved the answer through embedding your option in a subquery. – honour nwagwu Nov 02 '13 at 12:25

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