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From "Carsten Ziegeler" <cziege...@sundn.de>
Subject AW: [C2] Sitemap Components, Content-Negotiation and Caching
Date Tue, 08 May 2001 06:57:32 GMT
> Donald Ball wrote:
> 
> On Mon, 7 May 2001, Carsten Ziegeler wrote:
> 
> > > > The Problem
> > > > ===========
> > > >
> > > > Multiple sitemap components within a pipeline may consider multiple
> > > > aspects ("dimensions") of a request. A HTTP server must/should tell
> > > > the client (be it user agent or cache) which aspects the delivered
> > > > data depends on. The means to tell this is the HTTP/1.1 "Vary:"
> > > > header.
> > > >
> > > > However, there seems to be no mechanism in Cocoon 2 by which the
> > > > components can set the "Vary:" header in a cooperative fashion to
> > > > correctly reflect all considered aspects.
> > >
> > > naively speaking, i'd reckon that it'd be the job of the 
> cache manager to
> > > set the HTTP/1.1 Vary header. components can (and do, right?) tell the
> > > cache manager what variables upon which they vary. i think 
> right now it's
> > > done on an ad hoc basis throughout the components. i reckon 
> carsten would
> > > know a bit better?
> > >
> > Yes, this is correct. Each component knows on which aspects it depends.
> > So this component is currently responsible for setting the 
> correct headers.
> > For example the BrowserSelector sets the "Vary: User-Agent" header etc.
> > If a component depends on other values it has to set them by 
> itself. This
> > is the only working solution right now.
> 
> but the components _do_ tell the cache manager what variables they vary
> on, right? so it should be possible for the cache manager to take over
> this job?
> 
Yes, the components give the CacheValidity objects to the manager, telling
on what variables (input) they vary. 
But the manager has (currently) no knowledge about these objects. They
are never checked or something like that. This might be a useful extensions
to the current manager.

carsten
> - donald
> 
> 
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