XML = e'''X'''tensible '''M'''arkup '''L'''anguage [http://www.xml.org/].

Very generally spoken it is a simplified form of [SGML], but stricter (more regular) in some aspects:
   * Singleton elements must end with />
   * attribute values must be quoted

Example:
 <father name="Jack" att1="1">
   <child name="Tom" born="1997" />
 </father>

"Programming XML in Tcl" [http://www-106.ibm.com/developerworks/webservices/library/ws-xtcl.html]
surveys the state-of-the-art as of spring 2001, mainly from a [Zveno]-biased perspective.

One deficiency of that article is its neglect of [Jochen Loewer]'s [tDOM] work.

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One way of specifying the valid tag structure of a class of documents is to use a Document Type Definition, [DTD] for short. This way was inherited from SGML. There are alternative ways ... XMLSchema, Relax(NG), ...

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Perhaps the single most important introductory point to make to Tcl
developers about XML is that it's built-in!  Almost--while the core
Tcl distribution doesn't know about XML, it does have excellent
[Unicode] abilities. The [Kitten] [starkit] includes an XML package while the
[ActiveTcl] installations of Tcl can easily add an XML package via [teacup].



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tDOM builds-in a pretty-printing serialization option.  Those with an interest in a comparable function
for TclDOM are welcome to try/use/improve/... dom_pretty_print [http://phaseit.net/claird/comp.lang.tcl/dom_pretty_print.html].
"[XML pretty-printing]" will eventually have more on this topic.

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How can you start to generate your own XML documents with Tcl?  In
answering just that question in a mailing list [[reference?], [Steve Ball] succinctly
advised, "When creating XML, I generally use [TclDOM].  Create a [DOM] tree in memory,
and then use 'dom::DOMImplementation serialize $doc' to generate the
XML.  The TclDOM package will make sure that the generated XML is
well-formed.

Alternatively, XML is just text so there's no reason why you can't
just create the string directly.  Eg:

        puts <document>$content</document>"

The problem with this is that (a) you have to worry about the
XML syntax nitty-gritty and (b) the content variable may contain
special characters which you have to deal with.

There are also some generation packages available, like the '[html]'
package in [tcllib] (this will be added to TclXML RSN, when my
workload permits)."

[DKF] - If you're going for the cheap-hack method of XML generation mentioned above, you'll want this:

  proc asXML {content {tag document}} {
     set XML_MAP {
        < &lt;
        > &gt;
        & &amp;
        \" &quot;
        ' &apos;
     }
     return <$tag>[string map $XML_MAP $content]</$tag>
  }

Naturally, the ''XML_MAP'' variable is factorisable... [MHo]: Why not using '''html::quoteFormValue''' for this purpose?

For generation of XML (HTML) the pure Tcl way, have a look at the xmlgen module
of TclXML on sourceforge: http://sourceforge.net/projects/tclxml/.
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If you want to get particular about entity encoding '''arbitrary text''', this is working for me:

 variable entityMap [list & &amp\; < &lt\; > &gt\; \" &quot\;\
        \u0000

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%| [Category Data Serialization Format] | [Category XML] |%
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