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Message-ID: <409C90D8.9090907@inf.ethz.ch>
Date: Sat, 08 May 2004 09:48:40 +0200
From: Andreas Frei <frei@inf.ethz.ch>
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To: Avalon Developers List <dev@avalon.apache.org>
Subject: Re: OSGi and Merlin?
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Hi,

OSGi is an initiative of the OSGi Alliance (www.osgi.org) which 
specifies a minimal service infrastructure. Its initial intend was to 
define a middleware for mobile infrastructure (OSGi = Open Service 
Gateway Infrastructure) back to '99 when it started. A new specification 
3 has been released in march 2003.
This specification defines different services which can be bundled and 
run in the core framework. The core framework is very similar to merlin. 
It is also a component and service management platform where bundles are 
the unit of deployment. Instead of using xml to define containers and 
components this information is directly encoded into the manifest. For 
example to export a package you define Export-Package=.... or 
Export-Service= for services. Services are then registered inside a main 
class which implements a BundleActivator with start(BundleContext) and 
stop(BC). Each bundle is loaded by its own classloader, through the 
manifest information classes can be loaded from other bundles.
I know of four open source implementation, knopflerfish, oscar, equinox 
(the core of the new eclipse), and one from ibm.
Impressive is its size for example knopflerfish uses about 200 kB!

So the core of osgi has nothing to do with Jini, but OSGi defines two 
discovery services, Jini and UPnP which can be plugged in when needed. 
Actually such a service defined by OSGi could also be adapted a bit an 
plugged into a merlin container.

cheers,
Andreas

pnb@scancoin.se wrote:

>Hi,
>I just stumbled over
>http://oscar-osgi.sourceforge.net/ and wonder wether anyone has any
>experience with OSGi as the service distribution layer (is that comparable
>to the Jini ifrastructure discussion earlier?)
>
>Looks a lot like if components/ containers could be distributed via that and
>that multiple Merlin instances could make up a dirstributed OSGi system?
>
>/peter
>  
>
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