- From: Fred Zemke <fred.zemke@oracle.com>
- Date: Fri, 09 Jun 2006 00:13:05 +0000
- To: public-rdf-dawg@w3.org
10.1.1 Projection The last sentence of the formal definition uses set notation for the result of projecting a solution sequence into a new solution sequence. This is not desired, because: a) sets are not ordered, but solution sequences are b) sets do not permit duplicates, but the intent is that the result of a projection might have duplicates. This can be corrected by using some notation denoting a sequence. Earlier we used (S1, ..., Sn) to denote a sequence, and that could be done here, for example, ( (project (S1, VS), ... project (Sn, VS) ). Or we can use the mathematical definition of a sequence as a function whose domain is the positive integers, in which case the sequence is represented { (i, project (Si, SV) ) | i = 1, ..., n } 10.1.3 ORDER BY The formal definition does not support the following features: a) ordering in descending order b) ordering by multiple sort keys. Fred
Received on Friday, 9 June 2006 05:40:16 UTC