- 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>
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 UTC