Trip Report (Oct 2001)

[Denys Duchier]

I was in Sweden for a week and I'd like to report on some of the
exciting developments that I discovered or discussed with our friends
in Stockholm.

1. MOZART FOR PEER-TO-PEER APPLICATIONS

As you probably know, the SICS research group is gearing up for P2P
applications.  They have secured important research constracts in the
area.  While I was there, Sameh (http://www.sics.se/~sameh/index.html)
managed to compile and demonstrate Mozart on a PDA (Compaq IPAQ).
I'll let him make an official announcement, but I find this very
exciting.  Soon, we will be able to announce Mozart for the ARM and
open up an entirely new area of applications.

2. DISTRIBUTION SERVICES FOR EVERYONE

The ideas underlying distribution support have matured.  The new goal
is to provide distribution services in a more orthogonal as well as
language-independent way: thus, languages other than Mozart may easily
acquire the same support for distribution, furthermore, the
distribution characteristics (choices of protocols) will be decoupled
from the datatypes.  Currently, the plan is to aim for providing
support for both Mozart and Java.  I'll let Per make an official
announcement if he cares, as this is essentially his baby.  Again, I
find this new direction extremely exciting and congruent with our
general interest in assembling specific language implementations from
general and reusable modular services.

3. STATIC INTERFACE CHECKING FOR LARGE MODULAR APPLICATIONS

Kostja (who, believe it or not, it actually again programming in Oz
these days _and_ likes the Oz debugger, Hooray! :-) suggested that
static checking for interface conformance would be of great benefit
for developing large projects.  I started implementing a tool for
performing such checks.  On my return to Saarbrücken, I talked to
Leif, and we have a preliminary plan for extending the compiler to (1)
first provide additional information to support the process, (2) use
this information effectively, (3) incorporate my tool when it is
ready.  This extension will be entirely optional, but I also believe
that cross-module interface conformance checking will be of great
practical benefit for software development in larger projects.

4. SYSTEM THREADS AND NON-BLOCKING SERVICES

It turns out that the development group at SICS is also interested in
this idea which I started to investigate not so long ago.  Therefore,
we decided to join our efforts.  I proposed a plan which distinguishes
several levels of abstractions.  We will begin by designing very
abstract specifications for the following services: (1) IO (2)
processes.  What we ultimately want are services that (1) guarantee
that the Oz emulator will not block (2) ensure progress.  IO and
processes are also two areas where Leif and I have long wanted to port
what I did in the contribs for Unix to Windows: this may be the better
way to achieve it.  The ultimate goal is to take all the gruby
complexity OUT of the emulator and provide it instead as very clean
plug-ins (factored out into services).  The short-term goal is to
provide non-blocking versions of such system calls as "connect".  My
ambition is to also provide an abstraction that will make it easy to
interface with existing libraries (where calls may block or last
forever in the case of libraries with their own processing loop).

5. QHTML: APPLICATION GUI IN A WEB BROWSER

Sameh gave me a demo of Donatien's QHTML.  This is a very cool tool.
In particular, it makes it possible to provide your application's GUI
entirely and transparently through a web browser... Unfortunately, the
current implementation is limited to IE Explorer.  I hope we can
motivate Donatien to extend his wonderful tool to support additional
browsers wherever possible.

6. BETTER INFORMATION AND TRANSPARENCY OF THE DEVELOPMENT PROCESS

There is indeed a lot of great stuff happening at SICS, yet none of it
is visible.  I have encouraged our Swedish friends to more actively
publicize their developments; in particular, I expect that Sameh will
soon announce the ARM port.  However, feel free to add your voice to
this encouragement (e.g. there are (white) papers, yet none of them
are available online).  Secrecy or mere opacity is extremely
detrimental to the project.  Let's keep everyone (including the user
community) abreast of the truly exciting developments that are
currently going on.

After discussion with Seif, we have agreed that the `hackers' list is
also the right forum for what Seif had in mind when he suggested the
`ideas' list.  The slightly revised declaration of intent is as
follows:

users at mozart-oz.org
        as it is now. intended for general mozart-related discussions.
        this list is publicly readable, but posting is moderated.

hackers at mozart-oz.org
        for discussions among designers and implementers.  This list
        is publicly readable (thus ensuring transparency of the
        development process), but posting is limited to developers
        (and selected individuals).

internal at mozart-oz.org
        for discussions internal to the consortium or non-public
        discussions among the designers and implementers.  This list
        is not publicly readable and posting is limited to the
        developers.

The internal list should be used only _very_ rarely.  All design
discussions should take place on the hackers list (or the users list
if a broader discussion is desired).  The purpose of the hackers list
is NOT to inform the public; it is to allow discussion among designers
and developers.  The fact that it is publicly readable merely ensures
that technically aware members of the public can gain insight into the
development process and our plans for the future.

There was much more, but I'll sign off for now...
Cheers,

-- 
Dr. Denys Duchier			Denys.Duchier at ps.uni-sb.de
Forschungsbereich Programmiersysteme	(Programming Systems Lab)
Universitaet des Saarlandes, Geb. 45	http://www.ps.uni-sb.de/~duchier
Postfach 15 11 50			Phone: +49 681 302 5618
66041 Saarbruecken, Germany		Fax:   +49 681 302 5615
-
Please send submissions to hackers at mozart-oz.org
and administriva mail to hackers-request at mozart-oz.org.
The Mozart Oz web site is at http://www.mozart-oz.org/.