Re: ISSUE-48: Less verbose delete syntax

On 9 Nov 2009, at 22:15, Andy Seaborne wrote:
> On 09/11/2009 20:27, Steve Harris wrote:ILTERs
>> I'm not so sure, FILTERs don't feel any less complex than OPTIONAL  
>> and
>> friends.
> Don't understand - how can a filter over a BGP be as complicated as  
> one of the binary graph patterns?

Well, it's just as disallowed in the template side, so the pattern  
still needs to be transformed. Admittedly it's FILTER -> nothing, but  
it's still some transformation work.

> A FILTER accepts or rejects rows of the query solution table, but  
> does not change the shape of a row which is determined by the BGP.

Well, it's surely a matter of perspective whether that's more or less  
complicated. I think in terms of joins, so FILTER seems more complex.

>> If we're going with simple lets just have templates (BGP + GRAPH).
> GRAPH is OK - same as with FILTER because the pattern is still a  
> fixed shape (no irregularities).

Well, in any case we still need to allow for


CONSTRUCT can do that, so it's well defined.

> We ought to change CONSTRUCT to align with that.


> We ought to formalize the query forms : CONSTRUCT can be done with  
> the "substitute(pattern, μ)" operation in Q-1.1

Yup. Modulo some stuff around unbound variables.

- Steve

Steve Harris, CTO, Garlik Limited
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Received on Tuesday, 10 November 2009 06:44:51 UTC