Questions on the caching sections of the spec

While reading the current WSRP draft and the HTTP spec I noted some 
differences between caching defined in WSRP and in HTTP. Can someone 
please explain why WSRP derives from HTTP in these points:

- a producer cannot specify that a piece of markup must not be cached

- 6.2.1.1 states: "Portlets indicating the cached markup can be used 
SHOULD also supply a new CacheControl structure with a new expiry for 
the markup. "
shouldn't it also state that the validation token should be set and that 
the current validation token should (or even must) be reused? If the 
producer sets a new validation token for the cached response, how does 
the consumer know which validation token to replace?

- 6.2.1.2 states: "Consumers should be aware that invoking 
performBlockingInteraction and/or handleEvents may cause cached markup 
to become invalid. "
doesn't this need to be stronger? I would have expected at least a 
SHOULD. How can otherwise the producer expect to be called with 
getMarkup after an action that invalidates the cache entry?

- why is the concept of HTTP weak validators that allows to have the 
same validation token for slightly different content not supported?


Thanks.

Stefan