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Re: Use of XML ?

On Tue, 31 Jul 2001, Eric Bohlman wrote:

> Because not all cases of data exchange occur between systems over
> which one person or group has control.  In your example, the transport
> format is directly coupled to the internal representation the two
> systems use for their data.  That's all well and good if the same
> people implemented both systems, but it starts to break down if, say,
> one of the systems is implemented in Java and the other isn't.  XML
> comes into play when you want the transport format to be independent
> of the internal details of how the data is processed.  By adding an
> extra layer of abstraction, you decouple the exchange process from the
> internal implementation details.  There are cases where for
> performance reasons you may not want to do this, but you really need
> to think carefully about them.

There's no real extra layer of abstraction, you could use Java class file
declarations (ignoring the method decls) as your schema language and
compile stubs in C that read and write serialised objects of that class as
structs - nobody ever bothered that I know of, but there's nothing
stopping 'em.

There are other endpoint-independent data formats that predate XML, too
(oh not that debate the XML learnt from SGML that's decades old again,
please?!?!? :-) such as XDR and ASN.1 and whatever CORBA uses.

XDR: http://RFC.net/rfc1832.html

ASN.1 (more complex, but with a "schema language" that puts XML schema to
shame, used heavily in telecoms systems): http://asn1.elibel.tm.fr/en/book/index.htm


                               Alaric B. Snell
 http://www.alaric-snell.com/  http://RFC.net/  http://www.warhead.org.uk/
   Any sufficiently advanced technology can be emulated in software