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   RE: [xml-dev] xml taxonomy

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You are both right.  To work at this problem, one has to 
start with XML 1.0.  Then the infoset, then schematization.
The notion of basing a system on well-formed strings doesn't 
begin with XML.  The notion that a formal system must have 
passive meanings doesn't begin with relational databases.

One might want to look at what is and is not formally 
expressible and by what forms (avoid the interpretation 
initially and just deal with the axioms and theorems).

It isn't useful to attempt to prove XML is as expressive 
as a relational database.  It can be useful to determine 
which kinds of theorems produce isomorphic meanings and 
those that can't.  For that, you XSLT is useful

For example, the object-oriented impedance mismatch is one. 
The rules for theorem creating don't enable attributes to 
have elements.  So a transformation from object languages 
where fields have object can't be done by transforming fields 
into attributes.  One has to transform the fields into elements 
at the higher level of the 'names'.  The meaningfulness 
is determined by the isomorphism. XML can express a programming 
language, but the forms are restricted by the formal properties 
of XML 1.0.

<aside>One of the reasons namespaces 
get a sense of revulsion is that they are a foreign system 
grafted into the grammar.</aside>

XML is a formal system with provable properties given that 
XML 1.0 provides the rules and the syntax.  I *believe* it 
is more expressive than a relational database 
but that this forces schematization to reduce the Boltzman 
entropy problem and in that way, is no different than 
the relational system.  Rules is rules.


From: Simon St.Laurent [mailto:simonstl@simonstl.com]

chiusano_joseph@bah.com (Chiusano Joseph) writes:
>one set might be xml with tags only - no attributes; another might be
>xml that is constrained to two levels; etc
>What value would there be to labeling these types of XML (e.g.
>"attribute-less" XML, "two-level" XML)? This seems to me to be
>something that can be better covered by an XML schema design (if we
>are talking about schemas here) than a broad classification. IOW, an
>organization/agency may decide for whatever reason that they want to
>avoid the use of attributes. It also appears to me that the
>combinations/permutations of the different aspects here can become
>quite extensive and perhaps unmaintainable.

I'm not sure I'd knock this so quickly - there's something interesting
here.  I suspect the math around this is already done, in the hedge
automata work that's underneath RELAX NG's pattern approach.  Exploring
this formally might not be as difficult as you suggest.

That said, I don't speak the math well enough to be able to say that for

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