- From: Graham Klyne <graham.klyne@zoo.ox.ac.uk>
- Date: Fri, 01 Oct 2010 09:56:42 +0100
- To: public-rdf-dawg-comments@w3.org
With reference to
http://www.w3.org/TR/2010/WD-sparql11-query-20100601/#optionals
http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#optionals
I think it would be helpful to add some explanation that
P OPTIONAL Q
and
P { OPTIONAL Q }
can yield different results. I recognize that to some extent this request
challenges the philosophy of what a specification is _for_, and accept that the
first purpose of a specification is to specify, but I also think that some level
of explanation helps to ensure the specification is properly followed. In this
case, both myself and at least one other experienced developer had not expected
there to be a difference.
For my own benefit, I've created an explanation based on elements of the query
algebra which you are welcome to copy and/or adapt if that is helpful:
http://code.google.com/p/milarq/wiki/OutstandingIssues#OPTIONAL_in_braces_doesn't_work_as_might_be_expected
#g
Received on Friday, 1 October 2010 08:57:41 UTC