On shared state

[Frank McCabe <frank.mccabe@us.fujitsu.com>]

I think that, on reflection, I stand by my original assessment of  
shared state vs shared views:

> I think that there are three things that are separate but related:
>
> 1. Shared state -- shared commitments, shared facts.
> 2. Views on the shared state. These are inherently not shared -- a  
> view is a view point of a participant.
> 3. Evidence -- messages which imply commitments, shared facts and  
> so on.
>

However, as this is a pretty technical issue, I think that it may be  
a good idea to add some wording to the text. Specifically, shared  
state is introduced in Section 3.2.3, line 478 but is not defined.

So, we could add the following text, replacing lines 481-485:

The shared state of a group of participants is the set of facts and  
commitments that is shared by the participants. What that means is  
that all the participants have access to those facts and commitments  
and they agree on them.

However, particularly when the participants are not in the same  
ownership domain, sharing state does not imply a common repository  
for that state. Instead, each participant has a view on its own and  
the world's state, including those aspects that are shared. A  
participant's view of the world's state is inherently private to the  
participant. I.e., there may be shared state but each participant has  
its own private view of that state.

There is a strong relationship between shared state and the  
interactions that lead up to that state.
Typically in the form of messages and other information that has been  
exchanged, this evidence is information that supports the set of  
facts and commitments that are shared.

It is not required that the interactions be recorded; although  
without such recording it may become difficult to audit the shared  
state and commitments at a subsequent time.


Hope that this helps ....

Frank