Re: Rigorously defining the interaction of conditional headers

On Thu, 5 Mar 1998, Roy T. Fielding wrote:

> 
> That can be added to the spec if desired, but the important thing is that
> the specification must define a precedence in order to avoid contradictions.
> Since precondition checks >> validation checks and etag checks > last_mod,
> the only sensible precedence is
> 
>     If-Match > If-Unmodified-Since > If-None-Match > If-Modified-Since
> 

This is certainly clear and simple.  But, why do precondition checks 
take precedence over validation checks?  While we are on the subject,
what is the purpose of the precondition checks?

John Franks
john@math.nwu.edu