RE: [Chicken-users] External representation for continuations

[Joerg F. Wittenberger]

On Thu, 2004-09-02 at 01:07, Jonah Beckford wrote:
> I see at least two main uses of serializing continuations.  The first [1] is
> to save a session so that you have a) a persistent Scheme environment, or b)
> an early LISP-ish way to distribute applications for those LISP-ish
> environments that do not have compilers.  The second [2] is to create a
> distributed framework or application.
[...]
> [1] a) is very cool as it would give you something like a long-running,
> persistent CSI interpreter; you definitely have to go down the function
> table or external info approach.  I guess this would be for those who like
> CHICKEN for its interpreter skills.  I definitely don't see a practical need
> for this, but in the same breath I definitely would want this.  It's the
> cool factor, but it sounds like a huge amount of work for little gain.
> 
> [1] b) is the hardest of all, but thankfully it is not necessary.  It is
> hard because the saved continuation must run on arbitrary platforms.  It is
> not necessary because CHICKEN has a decent compiler, which lets you
> distribute applications in a more portable way.

You might be interested to hear that www.askemos.org is basically a+b.
Moreover this "a" is in "virtual synchrony" (as the spread people would
call it) in a redundant p2p-distributed environment.

Jonah, you are right, it has been a lot of work.  But you are wrong
about the little gain!  The practical need is tamper proof processing. 
If you want to have a persistant process which has legaly binding
effect, let's say a voting machine, than you need to proof that the
machine is correct.  The only way I've seen, was to define an abstract
virtual machine (in terms of XML documents; but see SXML - that Scheme
in a way) and have a proxy network run byzantine agreements for each
state change of the process.  There are other uses, e.g. the german
supreme court for patent law found in 2002 that a publication on the
internet doesn't fullfil the requirements of a publication, since
there's no way to proof the timestamp.  For that reason the Askemos
object identifiers are self-verifying and include author, date and the
message.  For publications/deeds all you need is to create a process,
which rejects modifications...

best regards

/Jörg