[cap-talk] A Taxonomy of Current Object-Cap Systems

[Mark Seaborn]

Charles Landau <clandau at macslab.com> wrote:

> Mark Seaborn wrote:
> > Are you only considering pure capability systems?  Unix file
> > descriptors, and in particular Unix domain sockets could go on the
> > list.  The comparison would be useful, considering that sockets are
> > connection-based (unlike EROS/CapROS/Coyotos and typical
> > language-based objects) and often not message-based.
> 
> I don't see the distinction. EROS/CapROS/Coyotos capabilities can be to 
> objects that represent a session or connection.

But EROS/CapROS/Coyotos objects are not limited to being sessions or
connections.  An object can be shared between processes which can
invoke it concurrently, whereas byte stream connections usually can't
usefully be written to or read from by two processes at the same time.

With Unix domain sockets (the SOCK_STREAM kind), if you want to share
a concurrently-invokable object between two processes, you have to
layer a protocol on top of sockets and arrange for the same object to
be exported across two connections.

Mark