- From: Jonathan Robie <jonathan.robie@datadirect-technologies.com>
- Date: Mon, 18 Nov 2002 15:25:44 -0500
- To: "Bas de Bakker" <bas@x-hive.com>, <public-qt-comments@w3.org>
At 05:42 AM 11/18/2002 -0500, Bas de Bakker wrote: >Dear XQuery WG, > >In the new working draft you invite feedback on the new "order by" >clause. Reading the issue list, it seems to have been created because >of incorrect assumptions. In issue 155, I read: [[[ !!! SNIP !!! ]]] Hi Bas, To me, Issue 155 is not the main reason for moving to 'order by'. As you point out, there are other ways of achieving the same functionality, and I think there is probably no significant difference in the expressive power using 'sort by ()' or the 'order by' clause. A more compelling reason for 'order by' involves sorting of elements constructed by a FLWOR expression. In most environments, indexes are related to the input of a query, not to the output. The 'order by' clause makes optimization easier because it relates the order of the output directly to the order of the input sequences of a FLWOR expression. sort by (), on the other hand, requires an XQuery implementation to look at an element constructor in a return clause and determine the source of each piece of information before it can leverage indexes in the input source. I have not found a general algorithm to do this. >To summarize: I fail to see what common problem "order by" is supposed >to solve. If you want to solve a problem our users actually do have, >please spend your (limited) time on creating "group by" instead. I'm still not at all sure what a 'group' is or should be in the XQuery data model, or what class of problems your users want solved under the concept of 'group by'. Could you fill me in on how you see this? I'm not at all sure that we have time to consider new features at this point, but regardless of when we look at this, the more information we have, the better off we are. Jonathan
Received on Monday, 18 November 2002 15:26:45 UTC