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RE: text nodes of document in XDM

• From: "David Lee" <dlee@calldei.com>
• To: "'David Carlisle'" <davidc@nag.co.uk>, <xml-dev@l...>
• Date: Tue, 11 Jan 2011 13:19:15 -0500

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).

Similar for serializing external parsed entities.   To *me*  a "document" is
NOT "exactly what you want" ... rather a simple sequence.
Is this for backwards compatible to the INFOSET based XSLT1.0 and XPath 1.0
?
Or is there a reason, within the XDM model itself, why documents should be
allowed to have mixed content ... 

e.g. why is this allowed or "exactly what you want"

document { "1" , 2.5 , <foo/> , text { " text " }  , <bar/> }

If this is purely for generation of external parsed entities, and the
following sequence produces the same result, why allow anything but a single
root element in documents 

( "1" , 2.5 , <foo/> , text { " text " }  , <bar/> )


Thanks for any insight.

----------------------------------------
David A. Lee
dlee@calldei.com
http://www.xmlsh.org


-----Original Message-----
From: David Carlisle [mailto:davidc@nag.co.uk] 
Sent: Tuesday, January 11, 2011 4:31 AM
To: xml-dev@lists.xml.org
Subject: Re:  text nodes of document in XDM


On 11/01/2011 03:17, David Lee wrote:

> Q) Why does XDM allow text() children of document nodes, and in fact
> allow multiple element children of document nodes (If I read it right .)
>
> For example in XQuery this is allowed
>
> document { text { "text" } , <elem1/> , text { "text2" } , <elem2/> }
>
> I'm wondering what is the use-case that led to this ?
>
> My best "clue" is a recent question/response on xslt-list which made it
> clear to me that <xsl:variable> produced a document node, but it could
> contain parentless text nodes
>
> I certainly understand the desire for XDM to allow parentless text,
> element, and attribute nodes .
>
> but I don't understand the use case for document nodes containing text
> and multiple element nodes .
>
> Am I correct in presuming this is to support XSLT 1.0 (and perhaps by
> inference XQuery 1.0 ) which allowed this ?
> Is it a chicken&egg problem ?
>

in both xslt 1 and 2 the common construct
<xsl:variable name="x">
foo
<bar/>
baz
</xsl:variable>
creates a document node with three children, two text nodes and an element.

However XDM supports this not just for xsl:variable, xslt/xquery are 
designed to produce not only xml documents but what the xml rec calls 
external parsed entities, and a document node that can take text or 
multiple element children is exactly what you want for an external 
parsed entity.
> What is the rationale for allowing document nodes to contain children
> which are not parseable from Text XML ?
>
> Is this a critical feature to maintain in a round-trip XDM serialization
> specification ? ( Yes I realize I'm asking for an opinion not an
> objective fact).
>
> Thanks for any advice, opinions, or historical anecdotes.
>
> -David
>
>

David

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• Follow-Ups:
  • Re: text nodes of document in XDM
    • From: Michael Kay <mike@saxonica.com>
  • Re: text nodes of document in XDM
    • From: David Carlisle <davidc@nag.co.uk>

• References:
  • text nodes of document in XDM
    • From: "David Lee" <dlee@calldei.com>
  • Re: text nodes of document in XDM
    • From: David Carlisle <davidc@nag.co.uk>