Re: text nodes of document in XDM
On 11/01/2011 18:19, David Lee wrote: > Thanks very much for this explanation. > Do you (or anyone) know why with XQuery and XSLT 2 .0 and XPath 2.0 using > XDM as the data model instead of INFOSET, why a simple sequence isn't used > for this purpose ? > That is why create a document node with<xsl:variable> when a sequence seems > the more obvious choice (to me). "Why" questions are always very difficult. One can attempt an after-the-event rationale ("this is why I think the design we ended up with makes sense"), but if the question is "what was the sequence of decisions that led to this situation, and what was each member of the working group thinking when they concurred with each of those decisions", then it becomes impossible even for a professional historian to untangle the convoluted process that got us to where we are today. Firstly, the history of the data model is that XSL (as it then was) developed a model that was cognizant of the DOM and its strengths and weaknesses, and tried to do better. That was long before the Infoset. The Infoset was developed in full knowledge of the XSL model, and incorporated many of its ideas, but also added bells and whistles for people who (for example) wanted to retain CDATA sections and entity references. The fact that xsl:variable creates a document node was a rational choice for XSLT 1.0 where the tree of nodes was the only composite structure available. It's a less-than-ideal choice for XSLT 2.0, but was necessary in the interests of backwards compatibility. > Or is there a reason, within the XDM model itself, why documents should be > allowed to have mixed content ... > I think the language could have been made to work without this property. Again, if by "reason why" you are looking for a researched history of the actual WG decisions and their justifications, then I can't find that for you. It's possible (this is speculation) that the decision was influenced by persons unknown who felt that the rule in lexical XML that a document must have only one outermost element was artificial, unnecessary, and unlikely to appear in the final Recommendation. Michael Kay Saxonica
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