Reputation: 6644
I am creating an RDF graph by using SPARQL CONSTRUCT statement. Following is my query:
prefix map: <#>
prefix db: <>
prefix vocab: <vocab/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
prefix d2rq: <http://www.wiwiss.fu-berlin.de/suhl/bizer/D2RQ/0.1#>
prefix jdbc: <http://d2rq.org/terms/jdbc/>
prefix fn: <http://www.w3.org/2005/xpath-functions#>
CONSTRUCT {
map:database a fn:concat('d2rq:Database', ';').
map:database d2rq:jdbcDriver str(?o1).
map:database d2rq:jdbcDSN ?o2.
map:database d2rq:username ?o3.
map:database d2rq:password ?o4.
}
FROM <http://www.ndssl.vbi.vt.edu/epidl>
WHERE
{
<http://www.ndssl.vbi.vt.edu/epidl#NDSSLDB> <http://www.ndssl.vbi.vt.edu/epidl#driver> ?o1.
<http://www.ndssl.vbi.vt.edu/epidl#NDSSLDB> <http://www.ndssl.vbi.vt.edu/epidl#dsn> ?o2.
<http://www.ndssl.vbi.vt.edu/epidl#NDSSLDB> <http://www.ndssl.vbi.vt.edu/epidl#username> ?o3.
<http://www.ndssl.vbi.vt.edu/epidl#NDSSLDB> <http://www.ndssl.vbi.vt.edu/epidl#password> ?o4.
}
}
I have found that fn:concat() and str() functions are not working with SPARQL CONSTRUCT. Query is giving me an error. However above mentioned functions works properly with separate select statements like followings:
fn:concat()
prefix fn: <http://www.w3.org/2005/xpath-functions#>
select (fn:concat('d2rq:jdbcDriver', ';') AS ?p) where {?s ?p ?o} LIMIT 1
str()
select str(?o) from <http://www.ndssl.vbi.vt.edu/epidl>
where {<http://www.ndssl.vbi.vt.edu/epidl#NDSSLDB> <http://www.ndssl.vbi.vt.edu/epidl#dsn> ?o}
Please let me know how can I use fn:concat() and str() functions with SPARQL CONSTRUCT.
Upvotes: 3
Views: 5091
Reputation: 22042
The CONSTRUCT
clause in a SPARQL query can only contain graph patterns. Filters or functions can not be included.
To include the output of some function in your CONSTRUCT query result, you need to use a BIND
operation in your WHERE
clause that assigns the function output to a new variable, and then you can use that new variable in your CONSTRUCT
clause.
For example, to use the output of the STR()
function, you'd do something like this:
CONSTRUCT { ?s ?p ?string }
WHERE {
?s ?p ?o .
BIND(STR(?o) as ?string)
}
Upvotes: 4