xml-dev - RE: Object-oriented serialization (Was Re: Some questions)

[Vane Lashua <vlashua@RSGsystems.com>]

What's the point of defining "Point"? You are putting it in a context for a
processing engine to process. "Point" is meaningless by itself -- even
though it may be syntactly correct, in a context, with normalized attributes
and values -- without a specific processor that understands what a "Point"
is.

Let's say you want to type a value in XML. Easy. ...type="int" value="1"/> .
Or ...type="2Dpoint" value="2,2"/> (whether I say 2Dxvalue="2" 2Dyvalue="2"
is of no consequence). Both "int" and "2Dpoint" are defined somewhere else.

A Java or COBOL processor may be made to understand the type "2Dpoint", but
XML never will. It is not a processor any more than valid Java source code
is.

Vane

-----Original Message-----
From: Colas Nahaboo [mailto:Colas.Nahaboo@sophia.inria.fr]
Sent: Friday, December 03, 1999 12:11 PM

Vane Lashua writes:
> I think you're mixing apples and oranges.

I see it the other way: I try to make people realize that they are the same,
and the current artifical limits in the XML syntax make people stuble on
artificial syntax problems.

> An even simpler declaration of your example below -- and correct in XML --
> would be:
> <Point value="12in,2cm;RFFx,G0,B0" />

This is not XML. You invent a sub-language to describe the contents of the
value attribute. You will then need XML and a XML parser to understand the
outer XML, and you will have to invent and specify the inner language, and
design and implement the parser, which is *more* complex than an unified
"XML
2" language. (note that SVG did just that with the contents of the path
element :-). People tend to invent plenty of these sub-languages and
mentally
hide them under the rug, failing to see that the did not simplified
anything,
just made things more complex at more places in many different - and often
unspecified - ways.

> XML is a storage medium. Java source code is a storage medium. XML may
> contain Java source code syntax, as Java source code may contain XML
syntax,
> but both need processors to do more.

Yep, but if you look at my example, you could see that I got rid of any
sub-language!!! I only need an XML parser, nothing else at the parsing
level.
I still need the upper semantic level, of course, but at least I dont have
to
have plenty of different lexical parsers (and specs) to describe my data.
The SVG example is striking. To implement a SVG viewer, you need to have an
XML parser, plenty of other parsers to parse the sub-languages invented in
the
different attributes and contents of the SVG XML, including a full CSS and
HTML parser...

Note that I descibed only the object instances, NOT the classes structures
(this belongs to schemas, not to the XML level), and they are not java, they
could represent C++, common lisp, python,... objects!

--
Colas Nahaboo, Koala/Dyade/Bull @ INRIA Sophia,
http://www.inria.fr/koala/colas


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