[cap-talk] Value of 'copy on write' as attenuation mechanism.

[Rob Meijer]

On Fri, May 23, 2008 09:29, Neal H. Walfield wrote:
> At Thu, 22 May 2008 21:00:03 +0200 (CEST),
> Rob Meijer wrote:
>> If not for scenario 2, you could say that the data allocation should be
>> bound to the original data owner. However, given that Alice delegates a
>> 'read only' attenuation to Bob, allowing Bob or Carol to claim storage
>> in
>> her name would seem strange.
>>
>> Do you see my problem with fitting COW within the controled 'rw' based
>> attenuation patterns? I feel I not fully understand how COW should work
>> in a consistent and intuitive way for both the scenario's above.
>
> It seems to me that in both of your scenarios, Carrol should normally
> be accounted the storage, not Alice and not Bob.  The reason for this
> is that it is a service that only she profits from and no one else.
> (An example of a not normal situation is a transparent proxy.  In this
> case, the proxy would pay but that's not a problem.)

So basically would it be fair to state that COW is a composition pattern,
not an attenuation pattern? I'm still a bit confused about this, as coming
from a read/write base, COW would feel like an attenuation to me, while
coming from a read only base, it would indeed clearly need to be a
composition pattern. But I guess indeed that a composition pattern that
assumes read only would fit also if read-write were used and would result
in something that in use would in fact only feel like an attenuation.
I guess I need some time to let my brain adjust to the idea that COW of a
read/write is not attenuation.

Rob