from & from named

I have found a strange side effect of the rdf merge for building the 
default graph as shown in the example below:

select ?person ?topic ?src
from uri1
from uri2
from named uri1
from named uri2
where {
    ?person c:recommends ?doc
    graph ?src { ?doc c:subject ?topic }

If the value of ?doc is an uri, it may succeed, but if it is a blank 
node, it always fails because the rdf merge that produces the default 
graph has relabeled the blank nodes.

So depending whether the values of ?doc are uri or blanknodes in the 
target graphs, the query succeeds or fails. From a *user point of view* 
this is incomprehensible.


Received on Friday, 15 June 2007 15:20:08 UTC