Re: Reliable links [Was: Stab in the dark ]

Tony Sanders <sanders@BSDI.COM>
Date: Fri, 18 Mar 1994 21:23:02 --100
Message-id: <199403182020.OAA15469@austin.BSDI.COM>
Reply-To: sanders@BSDI.COM
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From: Tony Sanders <sanders@BSDI.COM>
To: Multiple recipients of list <>
Subject: Re: Reliable links [Was: Stab in the dark ] 
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"Daniel W. Connolly" writes:
> But in either case, you can give the same url twice and there's no
> mechanism to guarantee that you'll get the same thing back,
This is true with a given URL but note the folowing from the HTTP spec
where it talks about the URI: header:

    However, it is guaranteed that if an object is successfully retrieved
    using that URI it will be to a certain given degree the same object as
    this one.  If the URI is used to refer to a set of variants, then the
    dimensiosn in which the variants may differ must be given with the "vary"

    Syntax          URI: <uri>  [ ; vary = dimension [ , dimension ]* ]
    dimension       content-type[12] | language[13] | version[14]

    If no "vary" parameters are given, then the URI may not return anything
    other than the same bit stream as this object.

    Multiple occurencies of this field give alternative access names or

I think this addresses a lot of the points you made but even more important
it makes it clear that reliable references to bitstreams have been thought
about.  However, *MOST* references should not be reliable in this fashion.
For example, you almost always want a vary=language, vary=content-type.