[cap-talk] A challenge for membranes

[Kevin Reid]

On Feb 18, 2008, at 9:38, Jonathan S. Shapiro wrote:

>   1. In order for a membrane to operate properly, it must impose
>      a boundary that can only be crossed by traversal of that  
> membrane.
>      This can be generalized to strictly hierarchical arrangements of
>      membranes, but not to general graphs of membranes.

I question this claim.

I may be out of sync with current cap-talk terminology, but to my  
understanding a membrane does not completely confine an entity by  
definition (there is not necessarily a 'cell' as you put it).

The definition of a membrane as I know it is that it plays Caretaker  
for multiple capabilities, and rewrites introductions across the  
membrane so that the membrane does not permit the *creation* of  
connectivity bypassing the membrane (except as exempted by policy).

For example, a Horton 'tunnel' is a membrane, as I understand it; as  
an unconfined entity, I am still on one side of the membrane (unless  
I have some prior association with the other party). This membrane  
does not interfere with my ability to separately participate in other  
membrane-based protocols; it is completely independent.

The problems you want to solve may well require confinement-by- 
membrane, in which case please consider this purely a terminological  
quibble.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>