More on notations and MIME types

John Cowan cowan at
Thu Dec 3 19:55:11 GMT 1998

Simon St. Laurent scripsit:

> I still argue that notations are a waste of time based on the misguided
> notion that information about dependencies (of whatever type) actually
> belongs in the document.

Notations are equivalent in power to XML-Data/DCD datatypes, though.
Somebody (with capital S) thinks it's worth being able to say what
the (syntactic) type of the information in an element is, and doesn't
seem to realize that notations already *do* that job.

Note that specific values can be pushed off into the DTD or XSchema or
whatever as default NOTATION attribute values.

> Let the dependent pieces be self-describing (MIME or something better), and
> you'll have a far more manageable system.  Keep as little information in
> the document as possible, and remember that there are other tools out there
> that can describe non-XML data types.  XML can focus on XML, which is what
> is does best, and leave the rest of this out of it.

That seems not to be the case, or the database folks wouldn't be
howling for "data typing in XML".  Notations do the job they want.

> >> How
> >> would I apply a MIME type to an attribute?  More important, why one earth
> >> would I want to?  Seems like some pretty heavy overkill.
> >
> >To say what the internal syntax of the attribute value is.
> Er, yes, that's overkill, like I said.  Nuclear weapons to kill gnats and
> all that.  Seems like a schema could crush that gnat quite nicely, and even
> use MIME types if necessary, without resorting to notations.

Eh?  You asked why MIME types for attributes might be needed; I replied,
and that became another occasion to denounce notations in favor of
MIME types or nothing at all.  If your strictures apply to notations,
they apply to MIME types too.

Here's my potted version of notations vs. MIME types:

	Both provide names for syntactic encodings.

	Notations have local names (private aliases),
	whereas MIME types don't.

	MIME type names have internal syntax, allowing partial
	interpretation; notation names are opaque.

	MIME types reference a central registry with private-use
	extensions; notations reference a distributed registry.

(And now I know how to explain notations for the book!)

John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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