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How Can I Delete Triples containing blank nodes?

There are two ways to delete a particular blank node:

To refer to it via some properties or:
To convert it to it's internal "serial number", a long integer, and back.

Assume the following sample scenario:

Important Note: IDs of bnodes will vary from server to server and even from run to run on the same server, so the application should identify bnodes by properties before doing bif:iri_id_XXX tricks.

Clear the graph:


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

Done. -- 4 msec.

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.

Delete one pair of triples:


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

Done. -- 7 msec.

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.

Each bnode, as well as any "named" node, is identified internally as an 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.

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.
```

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.

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


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

Done. -- 4 msec.

So 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.

Now 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.

Three minus two gives one triple remaining:


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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