Questions about Update 1.1

I've been noodling on update today, and I have a couple of questions  
for people who've already implemented it:

1) If you have DELETE { <a> <b> ?z . <c> <d> ?z } what does that mean?  
The grammar allows it, but maybe it shouldn't? It could imply DELETE  
{ <a> <b> ?z . <c> <d> ?z } WHERE { <a> <b> ?z . <c> <d> ?z }, but it  
should be explicit what happens somewhere.

2) Can you delete bNodes with DATA? DELETE DATA { <a> <b> _:z }  
doesn't really make much sense. Some stores (including Jena and  
4store) allow you to quote bNodes like DELETE DATA { <a> <b> <_:z> }  
but that's non-standard.

Without DATA you can do something like:
   DELETE { <a> <b> ?z . <c> <d> ?z }
   WHERE { <a> <b> ?z . <c> <d> ?z . FILTER(isBNODE(?z)) }
but that's really inconvenient, and will be hard to optimise if you  
want to delete large chunks of data.

- Steve

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Steve Harris
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