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Comments on 10.1 "Solution sequences and result forms" (CR 6 Apr 2006)

From: Fred Zemke <fred.zemke@oracle.com>
Date: Fri, 09 Jun 2006 00:13:05 +0000
Message-ID: <4488BCD9.2060503@oracle.com>
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.

Received on Friday, 9 June 2006 05:40:16 UTC

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