W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > July to September 2005

Re: Updated SPARQL Query Results XML Format draft

From: Dave Beckett <Dave.Beckett@bristol.ac.uk>
Date: Thu, 14 Jul 2005 10:46:46 +0100
To: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1121334406.3567.10.camel@hedwig.dajobe.org>

On Wed, 2005-07-13 at 15:07 +0100, Steve Harris wrote:
> On Wed, Jul 13, 2005 at 02:59:45 +0100, Dave Beckett wrote:
> > However, I've also noticed a couple of items in Red Ink that still need
> > thinking about:
> > 
> > 1. How/if to record duplicates in results. (Section 2.3.3)
> > 
> > When ORDER BY is given, the result format may record index="1",
> > index="2" on the <result> element.  (Side issue - "may" or "should" do
> > this?)
> 
> I dont see the point to this really, but how does it interact with OFFSET?
> Shouldn't the count start from OFFSET + 1?

If we keep with this design, I guess so.
 
> > However when there are duplicates should it generate indexes 1, 2, 2, 3
> > where items #2 and #3 are duplicates?  (A query with ORDER BY but no
> > SELECT DISTINCT).
> 
> Strong "no" from me. Any numbering should be monotonic.

monotonic means order preserving right?  So 1, 2, 2, 3 does preserve the
order - if items #2 and #3 are duplicate results.  Otherwise order
information is lost.

The index="number" item was added because we added ORDER BY and before
we finished deciding what it would do.

Maybe you just need to know that the results are ordered - i.e. an
isOrdered boolean flag.   Is isDistinct also needed?  Those seem to be
the two crucial flags that tell you the four forms of variable bindings
results you can get:
  1. a bag (the default)
  2. an ordered sequence (ORDER BY)
  3. an ordered sequence with no duplicates (ORDER BY + DISTINCT)
  4. a set (DISTINCT)

  Refering to 10.1 Solution Sequences and Result Forms
  http://www.w3.org/2001/sw/DataAccess/rq23/#solutionsResults

unless the LIMIT and OFFSET indexes are important.

Dave
Received on Thursday, 14 July 2005 09:47:01 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:15:23 GMT