Re: [architecture] Geronimo and OSGi

[Jean-Bernard Stefani <Jean-Bernard.Stefani@xxxxxxxxxxxx>]

At 12:05 +0200 28/10/05, Pierre-Yves Gibello wrote:
> Christophe Ney wrote:
>
> > A smart person pointed out to me that things 
> > are moving on J2EE and  OSGi convergence.
> >
> > Will Geronimo be the first?
> Excerpt from one of the mails:
>
> "It will be a bi-directional integration, so 
> OSGi bundles will be able  to see geronimo 
> services and geronimo services will be able to 
> see  bundles (and services in bundles).  Using 
> your terminology it will be  a container."
>
>
> Looks like what Mikaël Desertot and Didier 
> Donsez are prototyping with JOnAS ? To my 
> understanding, they try at least to deploy JOnAS 
> services as OSGi bundles - thus embedding an 
> OSGi platform in the app server, as well.
> If so, it is even better integration that what 
> the Geronimo guys envisage (OSGI bundles and 
> Geronimo services should somewhat "see each 
> other", although JOnAS services might be OSGi 
> bundles ?).
>
> I don't know what is the position of the JOnAS 
> team regarding this, but I think we have a kind 
> of "Fractal vs OSGi" issue at OW (although I'm 
> not sure both approaches address the same 
> problem, and I'm not even sure they are 
> uncompatible).
>
> Mikaël, Didier, and François Exertier probably 
> have a more accurate understanding of all this 
> than I can have myself, but I think OSGi can 
> bring back some architectural consistency in the 
> OW projects... (although I agree it's quite a 
> bit late, Oscar has gone now).
>
> It's time for discussions and clear choices, 
> because the future of JOnAS will be dramatically 
> affected by what we decide these days.
>
> Regards,
> Pierre-Yves Gibello - ExperLog


Just a small reaction on one bit of creeping 
misunderstanding. Sorry to pick on you 
Pierre-Yves, but there is no 'Fractal vs OSGI' 
issue at OW in my opinion, only people who do not 
understand the difference between Fractal and 
OSGI. Also, lying beneath this sort of remark is 
the implicit statement that the 'insistence' of 
Fractal in OW is somehow preventing OW projects 
to use useful technology: This is just not true 
since no one to my knowledge has ever been forced 
to use Fractal. And the JOnAS tema is sovereign 
in deciding where he wants to go. But let's set 
the record straight once and for all.

OSGI is primarily a packaging technology. It only 
allows you to capture a small part of your 
software' architecture (via export and import 
clauses), and to deploy it locally.

It does not allow you to build a software whose 
architecture, expressed in terms of component 
containment and component binding relationships, 
would be introspectable and modifiable at 
run-time. It does not allow you to build you 
software using components with full-fledged 
meta-level operations for supporting 
cross-cutting concerns, non-functional behavior 
and on-line reconfiguration. This is what Fractal 
brings you.

So the question : 'should we use Fractal or 
should we use OSGI ?' is moot. If you only want 
to split up you software in manageable packages 
and deploy those packages, you can indeed use 
OSGI. It has the advantage of being a 
specification developed (over the past 6 years - 
and only now becoming noticed) by
an industry consortium, and therefore the next 
best thing to a standard these days.

If you are concerned about developing your 
software so that is has an explicit software 
architecture to help in software maintenance and 
upgrade, online management and reconfiguration, 
managing non-functional and cross-cutting 
aspects, then you should consider Fractal.

I definitely agre that some architecture debate 
is needed for the next generation of JOnAS, but 
would it be possible to have it with a clear view 
of the issues ? Also, I find it ironic that we 
always watch with interest
what the competition is doing, and do not pay 
serious attention to the more innovative ideas we 
might have inhouse.

Cheers,

Jean-Bernard
--

*************************************************************
Jean-Bernard STEFANI
Research Director, SARDES Project
INRIA Rhône-Alpes
655, avenue de l'Europe
Montbonnot
38334 St Ismier Cedex
France
tel : +33 (0)4 76 61 52 57
fax : +33 (0)4 76 61 52 52
email : Jean-Bernard.Stefani@xxxxxxxx
*************************************************************