[XSL-LIST Mailing List Archive Home]
[By Thread]
[By Date]
RE: [xsl] casting sequences
Subject: RE: [xsl] casting sequences From: "Michael Kay" <mike@xxxxxxxxxxxx> Date: Thu, 15 Jan 2009 15:54:22 -0000 |
> Yes, for that kind of expressions, I always miss the > ability to use the step operator on atomic values: > > tokenize(...)/xs:dayTimeDuration(.) > > Were there any clear reason the attempt floundered? > Not a clear reason, no: rather, in classic committee style, a sequence of decisions. Early on, various proposals were made using a new operator. Suggestions included "\", "->", "!". Some people didn't like the choice of operator, some people didn't see the need for the facility, and between them they defeated the proposals. "/" was also proposed, but (a) it was hard to reconcile the semantics with the existing "/" (as regards duplicate elimination and document order), and (b) people didn't like the fact that you would be able to write "40/5" and the result would be 5. Also (c), at that stage in the game there were still people arguing against the document-order semantics of "/", and those of us who wanted a simple mapping operator didn't want to lose the fragile consensus over the behaviour of "/"... At a much later stage, when XQuery vendors were starting to get feedback from real users, and when the meaning of "/" applied to nodes was no longer up for debate, IBM proposed allowing "/" as a simple mapping operator provided (1) that the lhs was a sequence of nodes, and (2) that the rhs was homogenous - either all nodes, or all atomic values. Despite being less orthogonal than an operator that allowed any sequence on either side, this won support because it dealt with most of the previous objections, because the timing was right, and because Don Chamberlin has the rare skill of presenting controversial proposals in such a way that the decision seems inevitable. That's the way committees work... Michael Kay http://www.saxonica.com/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [xsl] casting sequences, Florent Georges | Thread | [xsl] Remove a number at the beginn, Graeme Kidd |
Re: [xsl] Matching or selecting tem, George Cristian Bina | Date | RE: [xsl] Matching or selecting tem, Michael Kay |
Month |
Keywords