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   Re: [xml-dev] Web Design Principles (was Re: [xml-dev] Generality ofHTTP

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On Tue, 29 Jan 2002, Gavin Thomas Nicol wrote:

> The point really is that for data interchange, you can do things. Data
> formats can be standardized well (GIF et al. as you point out). For
> information interchange (i.e. data that has "meaning") it's much
> harder.

I'm interested in how you define the difference; the meaning of an image
is a pattern of light, the meaning of a purchase order is a request for a
purchase. We can manage the quite demanding case of encoding patterns of
light (it's not as easy as it seems), purely because there is enough
demand for a decent solution.

Take the PNG image file format; it stores the raw image data and all sorts
of other optional stuff - textual comments, information on the exact
relationship between the encoded numbers and levels of actual light (for
exact colour matching) or arbitrary units (for pseudocolour images
constructed from data sets), and so on...

There are things that are not in the base PNG standard, which have to be
defined as additional standards on top of it (it has an extension
mechanism for this, of course!). So competing standards for attaching porn
type codes to PNG files (y'know, 'MmF n/c dom' :-) might emerge.

Software reading these things would have to try to support as many
standards as possible, and software writing them may well end up
redundantly specifying the codes in more than one format to account for
readers that only understand one format. Either way, all those cases will
need to be seperately considered by the software developers; there is no
general way to automatically detect a variation on a known theme and try
to find a mapping, since the possibilities are too vast.

What can we do to fix this problem, in general? I dunno. But it won't be
easy and unless you have any really good ideas (anyone?) don't expect it
to be any better with XML!

I think the answer might have to be in what we use for a schema language -
if the schema is so formal and tightly specified in terms of semantics as
well as syntax that there is hardly any ambiguity in how to construct a
representation of some real-world object, then there could never be
competing standards. How to do this is left as an exercise to the reader.


                               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


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