5 Replies Latest reply on Jan 22, 2015 6:37 PM by alwu-Oracle

    blank nodes and describe queries

    M.R. Strand

      I am unable to make a post containing my problem. I get a message stating that "Due to span, this content is blocked".

      When I removed the examples, it worked. I dont know what example triggered your spam filter though. Hopefully the below text makes sense even without the examples.


      --- Trying here again: Removing all examples. .

      On other implementations of the SPARQL protocol, (i.e. Jenas TDB), a DESCRIBE query will return a model containing.

      1. The subject resource

      2. All resources connected to the subject with any property.

      3. If the resource found in (2) is a blank node, repeat (1) with that blank node as subject.

           Unless: A describe of that blank node has been done before.


      This ensures that blank nodes are usefull when using describe. If this is not the case, the resulting model is useless. For instance, we get the following answer (prefixes omitted)




      As you can see, the complex OWL restrictions, which uses blank nodes, are omitted.


      The same query using SEM MATCH, gives me, among other things, this line:



      I realize we can use this to create a PL/SQL method that iteratively builds a set of triples by following the bnodes, but I trust Oracle over myself to write that function efficiently.

      Is this something you are aware of and fixing, or will the task fall to me?