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The RDF Working Group is defining how blank nodes can be skolemized by a store. This can be used (internally) as a way to order blank nodes.

In addition, SPARQL 1.1 does provide a way to group related items, blank nodes included, together be using GROUP BY.

SELECT ?card ?adr ?pred ?obj {
  ?card a vcard:VCard; vcard:adr ?adr .
  ?adr ?pred ?obj .
} GROUP BY ?vcard ?adr ?pred ?obj

While this clusters RDF terms that are the same, it does not sort them.

Implementations are also free to provide extensions to "<" or ORDER BY to provide placing rows with the same blank node together in the sort order.

The working group did not choose to make changes in this area of the specification during the "Features and Requirements" phase and the working group charter discourages any change that would alter the results of a query that was valid according to SPARQL 1.0.

Therefore the working group has decided not to make a change in this area.

We would be grateful if you would acknowledge that your comment has been answered by sending a reply to this mailing list.

Andy, On behalf of the SPARQL WG