RE: NEW ISSUE: Methods and Caching (proposal)

Here's my proposal:

* Replace the first line of Part 6, section 3.1:

     - A correct cache MUST respond to a request
     - with the most up-to-date 

     + For methods other than GET and HEAD, a cache
     + MUST forward the request to the origin server
     + and MUST return the origin server's response.
     + For GET and HEAD requests, a cache MUST 
     + response with the most up-to-date
     
* Insert the following paragraph at the beginning of part 6, section 6
(Response Cacheability):

     + Responses for methods other than HEAD and GET
     + MUST NOT be cached.

* Remove part 6, section 13 (Write-Through Mandatory).

* Remove all the "responses to this method are not cacheable" statements
from part 2.

* Remove the statement about the cacheability of POST in part 2, section
8.5.

* Issue an errata or some other update of RFC 4918 that says that PROPFIND
responses are not cacheable.

Justification:

* This is the simplest thing that could possibly work.

* Nobody is caching anything other than GET and HEAD responses anyway.

* Section 13 is redundant with the other parts, and it has misleading
statements. For example, according to section 13, a cache cannot return a
5xx response if it cannot communicate with the server. 

- Brian