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RE: Streaming Transformations for XML

• To: XMLDEV <xml-dev@l...>
• Subject: RE: Streaming Transformations for XML
• From: Jandia Cyril <cjandia@l...>
• Date: Thu, 14 Feb 2002 12:29:48 +0100
• Importance: Normal
• In-reply-to: <3C6A8430.8020702@d...>

Hi again Petr ;o) - Hi all,

> From: Petr Cimprich <petr@g...>
> To: "'xml-dev@l...'" <xml-dev@l...>
> Subject:  Streaming Transformations for XML
>
> I'm playing with an idea of a streaming transformation language.
> [...]
> Petr Cimprich
> Ginger Alliance
> www.gingerall.com

Making the assumption STX will be useful on its own (as soon as precisely
described :-) here are some "day after" thoughts (in no particular order)
about it - in the hope of helping it, while keeping it as simple as it
is/possible :

I have a problem with your "stx:copy-of" operator.

Don't you think it would be quite difficult to give it precise and simple
semantics if you let it as it is now? I mean : under the form of an
**element**.

What's the point? Well, as I understand it now, it is free to appear (or
not) at beginning/end of a stx:template's child list. So, what happens if
you omit it in either of these template occurrences :

<stx:template match="element-start::an-element-type">
<stx:copy-of/>
...
</stx:template>

and

<stx:template match="element-end::an-element-type">
...
<stx:copy-of/>
</stx:template>

Then, I foresee you'll have to add many usage conditions for
restricting/controlling its appearance in context, in order for it to have
determistic effect, won't you?

Thus, I guess it would be more unambiguous to re-introduce it (from its
STX-transform-operator nature point of view) as an attribute : copy="yes|no"
;
now here's your transform sample, back, in STX, say "version 0.2" (which is
shorter/simpler) :

<stx:transform xmlns:stx="some_namespace_here">

  <stx:variable name="date" select="'Monday'"/>

  <stx:template match="element-start::list" copy="yes"
copy-attributes="all">
    <stx:attribute name="date" select="$date"/>
  </stx:template>

  <stx:template match="element-start::item" copy="yes">
    <id><stx:value-of select="@id"/></id>
    <stx:if test="@id=2">
      <note>the item we have been looking for</note>
    </stx:if>
  </stx:template>

  <stx:template match="element-end::item">
    <date><stx:value-of select="$date"/></date>
  </stx:template>

  <!-- and why not RegExp, BTW ?
  ("$1" in "<stx:value-of select..." gets its value from the regexp pattern
(in parenthesis) of
   "<stx:template match='...'") -->
  <stx:template match="character::(.*)">
    <text><stx:value-of select="$1"/></text>
  </stx:template>

</stx:transform>

Also, what do you think of this RegExp idea ? I like it.
But, am I not off topic (concerning envisioned STX simplicity) ?

PS :
Finally, I propose to add the following to your list of "SAX axes" :
"after-element-start::" (as a synonym of "element-start::"),
"before-element-end::" (as a synonym of "element-end::"),
and "before-element-start::", "after-element-end::" (for completeness).

Does all that make sense ?

Regards,
Cyril Jandia
http://www.cjandia.com/
Author of ESPX/TinyXSL
http://www.cjandia.com/2001/espx-tinyxsl/

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