> From W.Sylwestrzak@icm.edu.pl Fri Aug 20 15:04:41 1999
> Delivery-Date: Fri, 20 Aug 1999 15:04:41 -0700
> Return-Path: W.Sylwestrzak@icm.edu.pl
> Date: Fri, 20 Aug 1999 23:46:47 +0200
> From: Wojtek Sylwestrzak <W.Sylwestrzak@icm.edu.pl>
> X-Accept-Language: pl, en
> To: Joe Touch <touch@ISI.EDU>
> CC: wrec@cs.utk.edu, mbeck@cs.utk.edu
> Subject: Re: Taxonomy draft - web replication problems
>
> Joe Touch wrote:
> >
> > It seems like there are a few dimensions in which caching and replication
> > differ:
> >
> > Caching Replication
> >
> > what is copied server output server source
> > (as Micah observed, though
> > I would apply it to all replication,
> > not just mirroring)
> >
> > who initiates it client server
> > (unless push-
> > cached, which
> > blurs the line)
> >
> > how permanent is it temporary permanent
> > (managed by the server,
> > flushed or updated via overwrites
> > by the server)
>
> i think it's a good start summing up our intuitions so far.
> however for each of these definitions it would be relatively easy to
> find a counterexample. it might be premature to consider these now,
> but i'm sure we could give examples of mechanisms that copy server
> output but can hardly be called caching, are initiated by server,
> but are still considered to be caches etc.
The purpose of these definitions (or the matrix thereof) is
to provide a grounding for the base concepts. One thing
we know all too well in WREC is that there is:
- a counter example for every definition
- a(nother) definition for any phrase
The question is whether we can define caching and replication
sufficient to distinguish them for the taxonomy.
> > The difference between a mirror and a replica, IMO, is that
> >
> > a mirror is a copy of an entire server
> > a replicate is a copy of one of the files on a server
>
> but then we run into problem of defining what is an 'entire server' ?
"entire database" - a related collection of data.
I.e., mirror refers to the server,or collection, not the
individual items. A datum is replicated; the collection is
mirrored. (at least that's what I'm trying to convey).
Joe
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