HLL/INT: What is an object, anyway?

Rainer Blome rainer@physik3.gwdg.de
Mon, 19 Jun 1995 18:00:17 +0200

> > [rainer]
> [faré]

> > I want: `somewhat' standardized device drivers for the time and space
> > ressources.
> I'm not sure what you mean about standardized device drivers ...

the exokernel paper says somewhere that all the exokernel does is to
securely multiplex the cpu (that's time) and memory (that's space)
ressources.  that's what you said you want from a good os in your `why ...'
paper.  and some months ago, i observed that the os may be viewed as a
device driver for these two because that's what device drivers should do:
securely multiplex some hardware ressource.

by somewhat standardized i meant that the exokernel is not

> > That's the equivalent of Emacs in the field of OSs.
> I'm not sure what you mean about [...] Emacs either.

i meant analogon, not equivalent.

emacs is an extensible editor that works by providing some simple core features
(elisp types and interpreter) that only come to life by using a library
(all the el files).

the exokernel system is an extensible os that works by providing some
simple core features (aegis) that only come to life by using a library (the
exos fake unix).

> An exokernel is a second-order tool to dynamically link modules to the
> hardware.

your use of the term `xth order' confuses me a little.  by `order' i
understand `nesting level of applications of sths to other sths'.  could
you give your definition?

maybe this is debate about words.  until now i understand things the way
that aegis is the exokernel, not exos (the posix on top of ;).  but then
again i may be wrong.  exo- sounds like `on the outside of' which would
mean aegis is the inner kernel, whereas the user uses the exos
unix-emulation library (the exokernel?)  which relies on the inner kernel.
in this view, aegis would be first-order and exos second-order.

> And why restrict security to some [...] type-system [...]?

what type-system?  i don't see why one would be needed to securely
multiplex on this low a level.  i haven't read about spin, but aegis works
without one.

> Tunes is a higher-order unified secure module system.
So Tunes is a SYSTEM, OK.

> [...] it concerns all the layers of the system, ...
so we have layers, heh? :-) there will be a lowest software layer,
somewhere.  what will you call it?  *chuckle*

does simplicity demand that we have as few layers as possible?  we need
protocols/interfaces for the layers to communicate with each other.

> not just the hardware layer, [...]
??? i thought we were NOT concerned with hardware?

> Thus, Tunes will include more than an exokernel, an exo-exo-kernel,
> or even an exo(n)-kernel.
do you mean libraries, applications and such?

>>>  "anything whose semantics can be finitely coded into a Turing Machine".
>>  Oh, sh**.  Do we really need that?  I hope we don't.
>  You mean actually coding into Turing machines ?
i mean i'd hate to use a perspective that theoretical here.  i don't see
any practical use for it here.