[openbiblio-dev] Blank nodes in SPARQL and rewriting of blank node names

William Waites wwaites at googlemail.com
Fri Jul 30 10:40:49 UTC 2010

More detail in the ticket here:

But briefly I think I have discovered one bug and one implementation
choice that may be slightly problematic.

The bug is that when blank nodes (as opposed to variables) appear in
a SPARQL query they seem to behave differently depending on if they
appear in the subject or object position (haven't investigated predicates).
I think a blank node in the object position behaves like a variable and
in the subject position it behaves like a concrete thing. I think it should
behave concretely in both cases but am not sure.

The implementation choice has to do with reassigning blank node
identifiers which means that if I have a graph in my program in
memory that contains blank nodes, and I persist it in the store, I
can't use my memory copy to build queries that involve the blank
node identifiers against the store.


William Waites <wwaites at gmail.com>
Mob: +44 789 798 9965
Fax: +44 131 464 4948

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