Re: [Ietf-caldav] Last Call comment on Etag requirements in draft-dusseault-caldav-12

Lisa Dusseault wrote:
> Thanks for the input.  Speaking as a document author here, I'm confident 
> we've made a decent set of tradeoffs, balancing possible risks against 
> benefits, and attempting to minimize the risks too.
> 
> The basic risk is that any requirements related to ETags may conflict 
> with future requirements.  We've attempted to minimize this risk by 
> making only one requirement -- that servers MUST NOT return strong ETags 
> if they have changed the data provided to be stored.  We believe that 
> this requirement is quite within the spirit of ETag design.   We didn't 
> make any requirements about weak ETags, nor did we require any behavior 
> that future specs might make illegal.  Since today with HTTP it's 
> perfectly acceptable not to return an ETag at all, future requirements 
> on ETags would at least have to work with a huge deployed base of HTTP 
> servers that don't return any ETag on PUT responses.
> 
> Thus, any future ETag-related requirements that invalidated this CalDAV 
> requirement, would also conflict with the huge deployed base of HTTP.  I 

How so?

A potential requirement of an XyzDav spec to return ETags even though 
the content was rewritten wouldn't be in conflict with HTTP at all. It 
would just be impossible to implement a resource that's both compliant 
to CalDAV and XyzDav.

This is why I think CalDav uses the wrong approach. There's a simple way 
to give CalDav clients that piece of information and which is guaranteed 
to be compatible with other specs, and that's what CalDav should do.

Or, alternatively, it could just stay silent and let that other spec 
work out the solution, instead of trying to come up with a fait accompli.

 > ...

Best regards, Julian

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