Can I Delete Triples containing Blank Nodes?

There are two ways to delete a particular blank node:

  1. Refer to it indirectly, using some of its properties, or
  2. Discover and refer to it by its internal "serial number" or ID (in Virtuoso, bif:iri_id_XXX, a long integer). Important Note: IDs of bnodes will always vary from server to server, and often from run-to-run on the same server, so it is usually better to identify bnodes by properties than ID.

How to Delete Triples containing Blank Nodes

Assume the following sample scenario:

  1. Clear the graph: 

    SPARQL 
  CLEAR GRAPH <http://sample/>;

Done. -- 4 msec.

  2. Insert three blank nodes with two related triples each: 

    SPARQL 
  INSERT IN GRAPH <http://sample/> 
    { 
      []  <p>  <o1a> ,
               <o1b> .
      []  <p>  <o2a> ,
               <o2b> .
      []  <p>  <o3a> ,
               <o3b>
    };

Done. -- 15 msec.

  3. Delete one pair of triples: 

    SPARQL WITH <http://sample/> 
  DELETE
    { ?s  ?p   ?o } 
  WHERE 
    { 
      ?s  ?p   ?o ;
          <p>  <o1a>
    }

Done. -- 7 msec.

  4. Ensure that we still have two bnodes, two triple per bnode: 

    SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s ?p ?o 
    };

s                p        o
VARCHAR          VARCHAR  VARCHAR
_________________________________

nodeID://b10006  p        o3a
nodeID://b10006  p        o3b
nodeID://b10007  p        o2a
nodeID://b10007  p        o2b

4 Rows. -- 4 msec.

  5. Every node in the Virtuoso store, whether "named" or "blank" ("unnamed"), is identified internally by a long integer: 

    SPARQL 
  SELECT  (<LONG::bif:iri_id_num>(?s)) AS ?s_num ,
                                          ?p     ,
                                          ?o 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };

s_num                p       o
INTEGER              VARCHAR VARCHAR
_____________________________

4611686018427397910  p       o3a
4611686018427397910  p       o3b
4611686018427397911  p       o2a
4611686018427397911  p       o2b

4 Rows. -- 5 msec.

  6. The integer can be converted back to internal identifier. Say, here we try to delete a triple that does not exist (even if the ID integer is valid): 

    SPARQL 
  DELETE FROM <http://sample/>
    { 
      `bif:iri_id_from_num(4611686018427397911)`  <p>  <o3a> 
    };

Done. -- 5 msec.

  7. Should have no effect, because the "46..11" IRI has <o2a> and <o2b>, and was not requested <o3a>: 

    SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };
s                p         o
VARCHAR          VARCHAR   VARCHAR
__________________________________

nodeID://b10006  p         o3a
nodeID://b10006  p         o3b
nodeID://b10007  p         o2a
nodeID://b10007  p         o2b

4 Rows. -- 5 msec.

  8. Now let's try to delete a triple that does actually exist. Note the use of backquotes to insert an expression into the graph template: 

    SPARQL 
  DELETE FROM <http://sample/>
    { 
      `bif:iri_id_from_num(4611686018427397911)`  <p>  <o2a> 
    };

Done. -- 4 msec.

  9. This time, there's an effect: 

    SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s ?p ?o 
    };
s                p        o
VARCHAR          VARCHAR  VARCHAR
_________________

nodeID://b10006  p        o3a
nodeID://b10006  p        o3b
nodeID://b10007  p        o2b

3 Rows. -- 2 msec.

  10. Now we'll delete everything related to nodeID://b10006 subject: 

    SPARQL 
  WITH <http://sample/> 
  DELETE 
    { 
      ?s  ?p  ?o 
    } 
  WHERE 
    { 
      ?s  ?p  ?o .
      FILTER ( ?s = bif:iri_id_from_num(4611686018427397910) )
    };

Done. -- 18 msec.

  11. This should delete two of the previous three triples, leaving one remaining triple: 

    SQL> SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };
s                 p         o
VARCHAR           VARCHAR   VARCHAR
___________________________________

nodeID://b10007   p         o2b

1 Rows. -- 4 msec.

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