[Twisted-Python] pb.Cacheable doc question

[exarkun at twistedmatrix.com]

On 5 Oct, 08:09 pm, stephen.c.waterbury at nasa.gov wrote:
>First, the "PB Copyable: Passing Complex Types" doc is
>*great* and the examples are excellent -- my compliments to
>all who contributed!
>
>My question is about the pb.Cacheable section
>(http://twistedmatrix.com/documents/current/core/howto/pb- 
>copyable.html#auto9)
>-- specifically the first sentence:  'Sometimes the object you
>want to send to the remote process is big and slow. "big" means
>it takes a lot of data (storage, network bandwidth, processing)
>to represent its state.  "slow" means that state doesn't change
>very frequently.'
>
>I would think that the product of its size and its rate of change
>is the applicable metric -- i.e.:  the bigger the object is *or*
>the faster it changes (not the slower), the more applicable
>Cacheable is, no?

That seems plausible.  I wonder if the rate comment is motivated by 
something else, like the chance of the remote cache being out of date 
when the remote side wants to use some of its data.  This would increase 
with the rate of change, but I don't know if it really matters.  I 
haven't ever actually used a Cacheable myself, as far as I can recall.

Jean-Paul