Re: [xml-dev] What is @xml:space about?

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

At 2012-07-10 11:36 -0400, John P. McCaskey wrote:
>On 7/10/2012 11:00 AM, Michael Kay wrote:
>
>>I don't know of any applications that use this attribute for any 
>>purpose other than to decide whether whitespace-only text nodes 
>>should be preserved,
>
>For stripping whitespace-only text nodes, <xsl:strip-space> would be 
>more efficient and would avoid counting such nodes with count(). Yes?

Perhaps ... though I think the stylesheet writer should simply be 
aware of the document model and not rely on any automatic stripping.

>The examples in 2.10 White Space Handling seem good, viz., use 
>xml:space='preserve' for source code and poetry, things that in 
>(old) HTML would naturally get put in <pre>. I'd have thought using 
>xml:space as intended would not be rare. It seems a pretty useful attribute.
>
>I see that XALAN lets xml:space=preserve override xsl:strip-space 
>(http://xml.apache.org/xalan-j/xsltc/xsl_whitespace_design.html). Is 
>that in a spec?

Yes, see http://www.w3.org/TR/2007/REC-xslt20-20070123/#strip where it reads:

  A whitespace text node is preserved if either of the following apply:

  The element name of the parent of the text node is in the set of
  whitespace-preserving element names.

  An ancestor element of the text node has an xml:space attribute with
  a value of preserve, and no closer ancestor element has xml:space
  with a value of default.

>Do all XSLT processors do that?

I believe they should all follow the spec and have 
xml:space="preserve" override xsl:strip-space.  I don't think a 
stylesheet writer should override a user's claim that their data has 
significant white-space-only text nodes.  If a user states that their 
element content white space nodes "mean" something to them, then I 
don't think any implicit or explicit stripping by the stylesheet 
writer using directives should touch them.  Of course the stylesheet 
writer can choose to ignore them in their logic, but not in any 
declarative pruning of the source node tree.

I hope this helps.

. . . . . . . . . Ken


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