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RE: APIs, messaging

On 23 May 2001, Simon St.Laurent wrote:

> > So does a tarfile, or source code for a programming language.
> Do you make any distinctions in the kind of functionality we're talking
> about?  Have you noticed that XML does really different things than
> those fine technologies.

Well, to make a less silly comparison, consider ASN.1: In 1984, it
provided a data format that can deal with unknown data turning up amongst
the data it expects from future versions of the protocol specifying new
fields, and it supports embedding of different "schemas" using a kind of

Consider any open file format (zip, PNG, etc) - they all have a mechanism
for delimiting chunks in the file, so that unrecognised types of chunks
can be handled. PNG/MNG goes way beyond XML's abilities in this
respect; chunks are flagged, so that a decoder seeing an unknown chunk can
find out if it's safe to ignore it or if it is crucial to the
interpretation of other chunks in the file.

Data formats that expect vendor extensions, varying versions of the format
in use in different places, and all that are old hat. It's just good
practice in design. XML enforces it, yes, but it's nothing new; this
starts to go back to that OO thread...


                               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