Subject: [xsl] The hard cocktail of sequence and (node-)set (Was: RE: RE: Postional predicates de-mystified) From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Fri, 4 Jan 2002 08:35:41 -0800 (PST) |
> > Curious about the shift from node-set to sequence then. > > Was it because of all the discussion (confusion?) on the list > > re sets? > > I think it started with the fact that XML Schema supports lists as a data > type, for example IDREFS is a list of strings. XQuery wanted to support > lists of nodes (without them, what is the result of a sort operation?), and > so came the idea of a data model based on sequences. There was then > considerable debate about whether the model should support sets and > sequences as separate types, with an eventual consensus that operations that > naturally produced sets (like path and union expressions) would be defined > as producing a sequence in canonical order, as this kept the model simpler. > > The confusion about XPath 1.0 node-sets may have had an influence. It wasn't > confined to this list either - I've heard people within W3C, people with a > mathematical training who should know better - claim that XPath 1.0 > node-sets were really sequences all the time. > > Mike Kay If not corrected this "feature" alone will become a classical example of bad design. I have pointed out elsewhere some of the unfortunate results of mixing these two very different datatypes into one: http://aspn.activestate.com/ASPN/Mail/Message/xsl-list/908998 Very regretful... Dimitre Novatchev. __________________________________________________ Do You Yahoo!? Send your FREE holiday greetings online! http://greetings.yahoo.com XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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