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Re: Some thoughts on XCAP's resource architecture

From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Wed, 24 Nov 2004 09:18:48 -0700
To: "Lisa Dusseault" <lisa@osafoundation.org>, "HTTP working group" <ietf-http-wg@w3.org>, "'simple@ietf.org'" <simple@ietf.org>
Message-ID: <opshy8xmdviz3etf0c9082f7@pail.measurement-factory.com>

On Sun, 2004/11/21 (MST), <lisa@osafoundation.org> wrote:

> the XCAP resource ontology and the URL addressing style that goes with  
> it shifts the HTTP design along two major axes:
>
> 1) Resource granularity
> 2) Dependency between resource

I disagree that HTTP defines some specific size and number of server  
resources (what you define as resource granularity). From HTTP point of  
view, URL paths are almost opaque. I agree that some server  
implementations are less suitable than others to support XCAP, but I do  
not see that as a showstopper. Will handling 1000 1-byte objects be as  
efficient as handling 1 1000-byte object with HTTP? No, of course not.  
However, handling 1000 1-byte objects may be efficient enough for a given  
application/environment. And if some proxy breaks while handling large  
number of small objects, that proxy is not HTTP compliant and should be  
fixed (to prevent DoS attacks and such).

I agree that HTTP assumes that resources are mostly independent. There are  
no HTTP mechanisms to, say, invalidate a large group of resources with a  
single response. However, individual applications and environments can  
deal with it. For example, Apache provides per-directory access controls.  
ICAP has ISTag header to invalidate all cached responses from a given ICAP  
server at once. These examples do not use HTTP features, but work fine on  
top of HTTP. Again, some existing server implementations would be less  
appropriate for supporting XCAP, but that should not be a showstopper for  
XCAP.

$0.02,

Alex.
Received on Wednesday, 24 November 2004 16:18:58 GMT

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