Attempted to address blank node issue in R2RML draft

I've tried to address ISSUE-30 in a new section of the draft:

Its contents are appended at the end.

There was a Usage Notes subsection on blank nodes; I merged its contents into this new section as both discuss the scope of blank nodes. Since it was the only usage note at this point, I removed the Usage Notes section for the time being.

This change might go a *little* bit further than what was indicated by my ACTION; if anyone objects to this text, please let me know ASAP and I'll revert to something uncontroversial.



Triples generated by an R2RML mapping can be placed into different graphs using rr:graph or rr:graphTemplate. Blank nodes in R2RML-generated triples are scoped to the single graph they appear in. The same blank node can never appear in two different graphs, named or unnamed. A single blank node identifier will create one distinct blank node for each graph that receives triples involving the blank node identifier.

This implies that triples generated from a single logical table row will have different subjects if the subjects are blank nodes and the triples are placed into different graphs.

Conformant R2RML processors MAY rename blank nodes when providing access to R2RML-mapped graphs. This means that client applications may see actual blank node identifiers that differ from those produced by the R2RML mapping. Client applications SHOULD NOT rely on the specific text of the blank node identifier for any purpose.

Received on Tuesday, 15 March 2011 21:05:53 UTC