Re: [Tclxml-users] dynamic XML

[Steve B. <Ste...@zv...>]

Maria M. Yu wrote:
> I am trying to test to see if I could use Tcl for dynamic XML as it's 
> claimed by tcltk.
>  
> Basically, I want to create a base xml document and then supply scripts 
> to fill in various parts of the base xml document with dynamic data.
>  
> Do you have anything that could help with my implementation?

I can think of a couple of different ways to achieve this.

Firstly, the simplest approach may be the "microscripting"
technique.  The technique involves embedding Tcl scripts in your
XML document and then use the 'subst' command to resolve the
scripts.  This approach was first developed for HTML documents
in the NeoWebServer and tclhttpd Web servers.  For example:

<article>
   <title>$title</title>

   <para>The time is [clock format [clock seconds]].</para>
</article>

Notice how the Tcl scripting and XML are intimately
tied together.

 From an XML purist point-of-view, another approach is to
use XSLT.  XSLT is very good at dynamically creating XML documents.
Parameters can be passed into the stylesheet as required.

Even more sophisticated is to use TclXSLT - XSLT combined
with Tcl extensions.

With TclXSLT you can make calls into Tcl scripts from an
XSL stylesheet.  The following example is a 'literal result element
as a stylesheet':

<article xsl:version='1.0'
   xmlns:xsl='http://www.w3.org/1999/XSL/Transform'
   xmlns:tcl='urn:my-tcl-extension'
   extension-element-prefixes='tcl'>

   <title><tcl:variable name='title'/></title>

   <para>The time is <tcl:format-time/>.</para>
</article>

The Tcl script(s) that implement the 'tcl:' extension
elements are not shown here.

This approach separates the Tcl code from the XML/XSLT document,
which is certainly a desirable characteristic.
However, you will notice that the overheads are high
so it is up to you as to whether that is acceptable.

There are other approaches - xmlgen springs to mind,
as well as using TclDOM to navigate and modify the document.

Hope that helps,
Steve Ball

-- 
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