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

Tony Sanders (sanders@BSDI.COM)
Fri, 18 Mar 1994 21:23:02 --100

"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"
parameter:

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.

--sanders