问题
I'm trying to understand how best to handle literals in Marklogic SPARQL data which may be in any case. I'd like to be able to do a case insensitive search but I believe that isn't possible with semantic queries. For a simplistic example I want:
SELECT *
WHERE { ?s ?p "Red"}
and
SELECT *
WHERE { ?s ?p "red"}
to return all values whether the object is "Red", "RED", "red" or "rED".
My data is from another source which has variable capitalisation rules. At the moment the only thing I can think of is to add an extra triple which always contains the text in lower case so I can always search on that value. Alternatively, would it make sense to create some new range query in MarkLogic with a case insensitive collation (if that's possible on triple data)?
回答1:
You could use a filter that ignores case.
select * where {
?s ?p ?o
FILTER (lcase(str(?o)) = "red")
}
Based on the answer to another question.
Edit: I asked Steve Buxton, MarkLogic's PM for semantics features, and he suggested this:
let $store := sem:store( (), cts:element-value-query(xs:QName("sem:object"), "red", "case-insensitive") )
return
sem:sparql('
SELECT ?o
WHERE {
?s ?p ?o
FILTER (lcase(str(?o)) = "red")
}', (), (), $store
)
sem:store is a MarkLogic 8 (now available through Early Access) function that selects a group of triples. The SPARQL query then runs on the reduced set, limiting the number of triples that need to be filtered.
来源:https://stackoverflow.com/questions/27255449/how-to-handle-case-insensitive-sparql-data-in-marklogic