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Re: Concerning LET or AS

From: Jeremy Carroll <jeremy@topquadrant.com>
Date: Mon, 02 Nov 2009 23:39:15 -0800
Message-ID: <4AEFDE23.7050109@topquadrant.com>
To: public-rdf-dawg-comments@w3.org
CC: Holger Knublauch <holger@topquadrant.com>, Jeremy Carroll <jcarroll@topquadrant.com>
PS

My example come from putting together the following thoughts ...
A suggestion that what people don't like about LET is that it is 
'procedural'.
However single-assignment is declarative, and that perceiving LET as 
procedural is a failure of understanding.
Ordering constraints can be declarative or procedural, LET introduces 
declarative ordering constraints.
The ordering constraints appear because of the shape of the problem: for 
example if you compute an end date from a start date and a duration, you 
need to know the start date and the duration.
Each LET declaratively but concisely introduces an ordering constraint.
The alternative SELECT AS WHERE construct declaratively and verbosely 
introduces an ordering constraint.

There is a natural ordering to do with the flow of information. This 
isn't necessarily the order of computation, but it is an order in which 
it is easier for the query author to think about the query. The LET 
syntax follows this natural ordering, the AS syntax does not.
Received on Tuesday, 3 November 2009 07:39:43 GMT

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