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   RE: [xsl] [Ann - Zvon] Templatotron

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Hi Miloslav,

Sorry to reply to this thread so late; xmlhack's posting reminded me to take
a closer look at this.

Are you familiar with the "literal result element as stylesheet"[1] feature
of XSLT? It seems that rather than trying to make Templatotron more
expressive by introducing instructions like t:choose, t:if, etc., one would
be better off using the simplified stylesheet syntax. However, there still
may be a place for Templatotron. I see Templatotron as a "simplified
simplified stylesheet". When working with a simplified stylesheet, it
sometimes becomes necessary to abandon the simple syntax because more
expressive power is needed, usually by way of applying template rules (which
you can't do in the simplified syntax). I've generally avoided the
simplified stylesheet syntax altogether because it ends up being more work
to switch the stylesheet's syntax (along with indentation) than to just use
the full syntax to begin with. This doesn't have to be the case if we have
an automatic way of converting from the simple syntax to the full syntax. In
fact, I think it would make sense to have two stylesheets that do this for
us, the first converting from "simple simple" (Templatotron) to simple, and
the second converting from simple to full.

When we find that more expressive power is needed, we simply drop into the
next syntax by applying the appropriate converter.

Templatotron template -> LRE as stylesheet -> xsl:stylesheet

To make Templatotron fit into this picture, I think it would need to be
radically simplified. I would get rid of the magical automatic namespace
aliasing (arguably bad practice and unnecessary in any case), introduce just
two attributes, t:for-each (alternative name to t:select) and t:value-of,
and interpret {} as an AVT in all attributes but the two I just mentioned.
In the end, only one namespace is used, only two attributes (and no
elements) are used in that namespace, and there will be no need for the "tn"
namespace whose purpose was to fill in the gap left by the automatic
namespace aliasing. Also, by requiring t:value-of when you want dynamic text
content, you eliminate the need for the ti:empty element. As it happens, all
of your tutorial examples can still be expressed using just t:for-each and
t:value-of, except for the one that uses a variable. The one that uses a key
can (as always) easily be rewritten using an XPath expression that doesn't
use keys. If you need variables, switch to LRE as stylesheet. If you
absolutely need keys, switch to full syntax. Etc., etc.

Templatotron inspired me to write a stylesheet that converts from the "LRE
as stylesheet" syntax to the full syntax (including indentation
adjustments). I posted the stylesheet to my website[2]. Having such a
converter around would make the simplified syntax more extensible and a
little more amenable to use.

To use an example from the XSLT 1.0 recommendation, my converter transforms
the following simplified stylesheet:

<html xsl:version="1.0"
    <title>Expense Report Summary</title>
    <p>Total Amount: <xsl:value-of select="expense-report/total"/></p>

into the following stylesheet using the full syntax:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns="http://www.w3.org/TR/xhtml1/strict"; version="1.0">

  <xsl:template match="/">
        <title>Expense Report Summary</title>
        <p>Total Amount: <xsl:value-of select="expense-report/total"/></p>


In the end, I'm not sure how practical or necessary Templatotron is given
that we already have the LRE as stylesheet syntax (which doesn't even
require a pre-process). Perhaps you weren't aware of the simplified syntax.
If not, I'd be interested in hearing if you think differently about it now.

Evan Lenz

[1] http://www.w3.org/TR/xslt#result-element-stylesheet
[2] http://www.xmlportfolio.com/desimplify.xsl

Miloslav Nic wrote:
> Templatotron  is a simple language for template based XML processing. It
> can be also thought of as a language designed to  save some writing in
> XSLT stylesheets and for keeping your attention focused on the
> XML syntax
> not on the XSLT one. I do  not personally mind the rather verbose XSLT
> syntax and so in my eyes the second point is much more important
> but there
> are  others who may appreciate Templatotron terseness.
> You will find Templatotron at:
> http://www.zvon.org/ZvonSW/Templatotron/Output/index.html
> There is a tutorial:
> http://www.zvon.org/ZvonSW/Templatotron/Output/page1.html
> and a reference:
> http://www.zvon.org/ZvonSW/Templatotron/Output/qr.html
> The stylesheet implementing Zvon Templatotron has about 100 lines and 3.5
> kB :
> http://www.zvon.org/ZvonSW/Templatotron/Output/download.html


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