[cap-talk] Tahoe visibly solving a problem with capabilities? (was: Re:Demonstration and engagement (was: If not God))

[Jed Donnelley]

On 4/15/2008 11:47 AM, Monty Zukowski wrote:
> On Wed, Apr 9, 2008 at 4:26 PM, Jed Donnelley <jed at nersc.gov> wrote:
>>  I say "close" because they haven't distinguished
>>  between read-only and "deep read-only".  For Tahoe
>>  it seems that (currently) the only read-only is
>>  "deep read-only".  Because of that I believe that
>>  I can't send you a read-only capability to a directory
>>  that contains some read-write files that I'd like
>>  to work on with you (there are other problems).
> ... 
> ... you want the ability to pass around a
> ReadWriteFile facet of a directory, which basically means only you can
> create new files and directories, but others can list and modify the
> files in that directory and subdirectories.

Hmmm.  I'm not quite sure of your terminology above, specifically
what you refer to as a "ReadWriteFile facet of a directory."  Also
I think of the creation of new files and directories as a distinct
issue.

What I do want is the ability for me to keep a writable capability
(facet) to a directory so that I can add and remove named capabilities
from it, while at the same time being able to send to colleagues
(e.g. working on a shared project) a capability to the directory
that will allow them to "fetch" full access to any of the capabilities
in the directory (e.g. writable access to a file or directory),
but not to modify the directory contents.

There are a few more details in this message:
"Sharing Tahoe file system directories? Loops, lost objects, etc.":

http://www.eros-os.org/pipermail/cap-talk/2008-April/010906.html

which almost overlapped with yours.

> Of course you could get by with just passing the caps to the
> read-write files individually; it just puts the burden on you to
> update the list when new files are added.

Right.  As noted above, with capabilities as data I could
also just store the capabilities in a file that I keep
write access to while giving out read-only facets to.
This brings up the issue about whether programs
written to the directory interface would be able to
make use of such files as noted in the above message.

--Jed  http://www.webstart.com/jed/