Subject: comments on draft-hoffman-char-lang-media

From: "Larry Masinter" <[email-masked]>
Date: Tue, 25 Apr 2000 14:49:32 -0700

In a private conversation about media features and
draft-hoffman-char-lang-media,
I thought that it became clear that we should suggest two clarifications on
the role of a 'language' and 'charset' tag registered in
draft-hoffman-char-lang-media; in particular, a 'language' feature describes
a preference (a client that can accept language=fr might also accept an
image of a sunset that has no language, or a multilingual document, etc.)
but that the 'charset' feature describes not only the ability to process
the particular charset but a stronger requirement, that the data be
delivered
as *labelled* with the named charset. So if you want charset=us-ascii, you
don't want charset=ibm367 (even though they're the same).

I think that we might want to consider revising the feature registration
BCP to encourage registrations to be clearer about whether a feature
represents a preference, capability, characteristic, and whether the
feature requires explicit labelling as such.

Larry

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From: Graham Klyne <[email-masked]>
Date: Wed, 26 Apr 2000 09:46:25 +0100

>feature requires explicit labelling as such.

Does this not presume that the distinction is wholely implied by the 
feature tag?

Use of colour, for example, might be a capability or a preference depending 
on the circumstances of its use.

This suggests to me that the distinction you draw should sometimes not be 
bound to the feature tag.

#g

------------
Graham Klyne
([email-masked])

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From: [email-masked]
Date: Wed, 26 Apr 2000 09:55:14 -0700 (PDT)

I agree with Graham here.  I believe it would be valuable to
be able to indicate whether a feature is a preference, capability,
characteristic, or lable, but I do not believe that could be
done at the time of registration.  In a bilateral exchange,
it will commonly be both a capability and a characteristic.
			regards,
				Ted Hardie

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From: [email-masked]
Date: Wed, 26 Apr 2000 10:45:46 -0800 (PST)

> don't want charset=ibm367 (even though they're the same).

I was meaning to bring this to Paul's attention -- sorry.

I believe it would be nice (and relatively easy) to address the language
tag issue in the draft. I don't insist on it, however, if people feel
this should be dealt with in the base specification.

However, IMO the latter issue
with charset aliases has to be addressed in the draft. (This is speaking
as an AD.)

But my take on the issue is a bit different from Larry's. (No longer speaking
as an AD.) I think that the document should say that aliases SHOULD NOT be used
in media feature expressions and that feature expression manipulation tools MAY
convert aliases to the the principal name for the charset.

I guess I don't see the point of insisting on pure label match semantics
here, as it doesn't fix the potential interoperability problem. I'd rather
simply say "don't use aliases" and allow correction of that error if
it comes up.

> feature requires explicit labelling as such.

I'm all for it if it's feasible, but my guess is that there are lots of
ratholes in the vicinity.

				Ned