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concatenationsparqlmarklogic

Concat values to use as subject in SPARQL Queries (MarkLogic)

I am attempting to do a SPARQL query in MarkLogic by concating my subject, predicate and object to use as a new "subject" node. I have attempted to do so with the query below

SELECT *
WHERE {
   ?subject </in/relationship/with> ?object .
   BIND(concat(?subject, "/in/relationship/with", ?object) AS ?relationship
   ?relationship </current/status> ?status
}

However, this query does not work as ?relationship now contains a string for each row resulting in the output of the query to be completely empty. Therefore, I am wondering if this can be done and whether it is possible to convert a string into a object that SPARQL can query with.

Solution

  • Stanislav is correct, you need to wrap the string in IRI(). Here a code snippet that runs directly in QC. Run it against an empty database to not pollute your other data:

    xdmp:document-insert('/triples.xml', <triples>{
  sem:triple(sem:iri("http://my/subject1"), sem:iri("/in/relationship/with"), sem:iri("http://my/subject2")),
  sem:triple(sem:iri("http://my/subject1/in/relationship/with/http://my/subject2"), sem:iri("/current/status"), "My status")
}</triples>)
;
sem:sparql('
  SELECT *
  WHERE {
    ?subject </in/relationship/with> ?object.
    BIND(IRI(CONCAT(?subject, "/in/relationship/with/", ?object)) AS ?relationship)
    ?relationship </current/status> ?status.
  }
')

    Whether this is a sensible approach might depend. Keep in mind that MarkLogic is particularly strong in keeping associated data together in documents, and you can embed triples, or use TDE to project triples out of them as well, allowing you to combine strength from document search, and keeping related data together, while still allowing to reason over facts with SPARQL.

    HTH!