Idempotent partial updates

Hi all,

HTTPbis has amended the semantics of PUT to be unambiguous in its
prevention of partial updates. I cannot understand the rationale
behind this change, and I have a couple of questions for the group:

- Given that 2616 was ambiguous, is it acknowledged that this
represents a breaking change to any existing infrastructure that
relies on PUT requests that are permitted to be partial?

- How is it foreseen that this over-specification of PUT will benefit
the web? i.e. what infrastructure will be able to exist once all PUT
requests are unambiguously non-partial?

- Is it acknowledged that this change will effectively prevent proper
idempotent partial updates on the web?

- In light of the recent proliferation of 'mobile clients' which
operate on relatively slow and unreliable networks where partial
idempotent updates would be ideal; is the loss of idempotent partial
updates considered acceptable?

Cheers,
Mike