Re: Nature of XML

[Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>]

Alexandre E. Kopilovitch <aek@vb1162.spb.edu> wrote:
: Georg Bauhaus wrote:
: 
:> : 3) about XML I'm still not sure. From its popular presentation it does not
:> : seem a programming language; but SAX somehow changes the picture.
:>
:> XML is a well defined term, and the hint it has in its
:> name is "markup language".
: Yes, but you did not notic?d the first letter -:)

Yes, but that's cheating :-)


:> SAX stands for Simple API for XML parsers, not a programming language.
: Ok, but constructing an input stream for an automaton is also programming -
: no less that constructing a transition matrix for it. And SAX produces exactly
: that - a stream of events... as far as I know.

Does an API produce something?

: Anyway, you excluded DTDs from your consideration, and that is the most
: suspicious thing there. DTDs certainly can't be characterized as simply
: "markup".

"<" followed by "!" starts a declaration, a markup declaration in
SGML reference syntax.  <!>, a comment declaration, is  the smallest
comment possible in SGML. So we have comments for a start.
There are DOCTYPE, ELEMENT, ENTITY, NOTATION, ATTLIST, and some
more kinds of declarations, among them marked sections, which
can be INCLUDED, or IGNORED, so we have conditional "compilation",
and maybe forward branching? :-)
Add some typing in ATTLIST and some constraints by IDREF(S). 
Then there is the treatment of (parameter) entity references.
Does it allow computations on strings? I don't know.

Here is add:

* The DTD

<!ENTITY x "1">
<!ENTITY y "11">

<!ELEMENT result EMPTY>
<!ATTLIST result
   value NMTOKEN #FIXED "&x;&y;">

* the document instance

<?xml version="1.0"?>
<!DOCTYPE result SYSTEM "add.dtd">
<result/>

* a "noncomputing" transformation that just shows the result.

<transform
  xmlns="http://www.w3.org/1999/XSL/Transform" version="1.0">

  <template match="result">
    <value-of select="@value"/>
  </template>

</transform>

(This is not XML at work, but the X you mentioned, in a sense :-)

-- Georg