Question on blank nodes

Hi,

I've been trying to find the conversation we've had on the scope of
blank nodes in a delete, but so far I haven't found it.

What happens for the following query:

  DELETE { ?s :p _:b } WHERE { ?s :p _:b }

Is the _:b treated as the same node in the template as it is in the pattern?

I know this was decided already, and I thought I wrote it into the
Update document. Unfortunately, it's not there, and just in case my
memory is not accurate I thought I'd better ask before putting it in.

Regards,
Paul