Re: Caching Servers Considered Harmful (was: Re: Finger URL)

Karl Auerbach (
Mon, 22 Aug 1994 22:01:20 +0200

> [Putting his publisher hat on]
> Because anyone running a caching server runs the dual risk of presenting
> out-of-date information to their users and can be in direct violation of
> international copyright law.

With regard to the first point:

-- With the pragma no-cache, the user's client software can force
the cache to fetch the latest version.

-- a client tool can look at the Date: line
of the document to see when it was taken from the original server. It turns
out that cache servers don't modify that date. (I wish that fortuitous
circumstance were hardened into the http specification.)
Anyway, with this ability, the user can determine whether a cached
document is sufficiently recent.

With regard to the second point:

-- There has been discussion of the copyright issue on the www-buyinfo

-- It will be necessary to build trust into caches. Publishers should
publish onto to those caches which they trust.

-- There is no good technical way to prevent copying once it reaches
the hands of the consumer in unwrapped form.

-- I've got some ideas (which you can find on the www-buyinfo archives)
which I'm going to present to a gathering of intellectual property
lawyers here in California to get their reactions.