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Re: setting a convention for property values

From: Nicholas Riley <njriley_at_uiuc.edu>
Date: 2002-12-04 22:36:02 CET

On Wed, Dec 04, 2002 at 03:08:11PM -0600, Jon Trowbridge wrote:
> In the long run, I think that namespacing properties is a losing
> proposition.

I agree. I'm trying to keep the implementation suggestions simple
under the hope that if it's simple enough, someone will just implement
it soon and the problem will be 'solved' for a while at least.

> To be really useful and to interoperate, we need to know more than if a
> chunk of data is binary or not. If we are going to have some metadata
> on our metadata, we should take it to its logical conclusion and have a
> way of attaching mime-type information to properties. That way a client
> could at least theoretically do the right thing with the data --- like
> pop up an image viewer when you ask to look at the PNG that you've put
> in a property.

Yeah, this is the ideal, but would require changes to the repos
structure, right?

> Even if binary properties are encoded in base64, the mime type should
> still be embedded in the prop in some systematic way.

I agree - how about just having MIME headers at the beginning of the
binary block? So it'd look something like this:

Content-Type: application/octet-stream
Content-Transfer-Encoding: base64

AAAAdGhpcyBpcyBhIHRlc3QK

One problem with that is that if somehow you'd want to retrieve the
MIME info without getting the entire property, it'd be a pain, and if
similarly, you want to have direct access to property URLs via WebDAV
it would also be a problem to pull that info out of the body and stick
it in the HTTP header.

But the ideal would be allowing attachment of arbitrary name/value
pairs, like properties, which -would- be constrained to being UTF-8.
This could get annoying if you had typed properties set on almost
every file because the metadata would be very repetitive, so it might
be nice to be able to define such properties with inheritance, or
repos-wide. This line of reasoning was what was scared me about the
complexity of the code required to implement such a scheme. The
madness has to stop somewhere :-)

-- 
=Nicholas Riley <njriley_at_uiuc.edu> | <http://www.uiuc.edu/ph/www/njriley>
        Pablo Research Group, Department of Computer Science and
  Medical Scholars Program, University of Illinois at Urbana-Champaign
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Received on Wed Dec 4 22:37:00 2002

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