W3C home > Mailing lists > Public > public-rdf-dawg-comments@w3.org > February 2005

RE: Questions about OPTIONAL

From: <jos.deroo@agfa.com>
Date: Thu, 24 Feb 2005 14:05:55 +0100
To: geoff@sover.net
Cc: andy.seaborne@hp.com, public-rdf-dawg-comments@w3.org
Message-ID: <OF0CEC7C08.2D89E9E1-ONC1256FB2.00467637-C1256FB2.0047F43E@agfa.com>

[...]

> That seems more like:
>                A and (B or true)
> than:
>                A and (B or not B) 
>
> You can't really simulate an optional without some form of not (NAF).

I still do the former, but that gives, as Andy says unhelpful answers.
I also did the latter a while back, but then in a monotonic way using
log:notIncludes, however a test case like
http://www.w3.org/2001/sw/DataAccess/tests/#dawg-opt-query-001
is then not giving that "Eve" solution (it works nicely for instance
when in the data :eve is used, but bnodes are existential variables
and ?SRC log:notIncludes {_:eve_0 foaf:mbox <#mbox>} is not the case).
I actually can't implement OPTIONAL 

-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Thursday, 24 February 2005 13:06:43 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 8 January 2008 14:14:47 GMT