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From Stephen McConnell <>
Subject Avalon Merlin - model-driven containment
Date Fri, 08 Aug 2003 23:28:22 GMT

Jason Dillon wrote:

> PS. Can someone write up something about the current state of the 
> major component containers out there with a feature blurb... no soap 
> boxes, just the facts jack. 

Based on current directions (and subject to the usual votes within the 
comming days) the Avalon community is about to release a container 
framework – codenamed Merlin. The framework deals with a set of critical 
container/component concerns that provide support for general component 
models (not just classic Avalon).

In particular, the Merlin framework includes:

* component meta info - declaration of a component criteria including 
configuration and parameterization requirements, contextualization 
requirements (including contextualization strategy, casting constraints, 
context entry requirements, optional and volatile entry criteria, 
etc.)., service dependencies, general component type attributes, logging 
criteria, etc.

* component meta data - definition of the meta model for declaration of 
component deployment directives that instruct a container with respect 
to deployment requirements - things like activation policies, 
configuration and contextualization information to be applied to 
components, lifecycle and lifestyle management and so on.

Combining the above two models together in a runtime environment enables 
the establishment of a model driven containment solution (the 
composition framework). Meta info and meta data can be supplied in 
either XML or serializable form, enabling remote model execution and 
management. Model execution is realized though the Merlin 'activation' 
platform which provides the infrastructure for nested component 
hierarchies, composite components (container that contain components the 
define an implementation strategy that allows a container to publish 
itself as a component), and the complete framework for configuration and 
context management based on a model driven approach. The Avalon work has 
already started on a JMX solution and with the introduction of the 
activation API, the Merlin platform will be able deliver a very 
significant level of management automation exposed via local or remotely 
accessible JMX management points that reach into fine-grain controls 
within the containment model.

Aside from all of the above - the Merlin platform provides a neutral 
component type discovery system and an automated component assembly 
framework. This ensures that the overall component deployment process 
can be simplified dramatically, in some cases down to nothing more than 
a couple of container directives.

The first public release of the Merlin platform should be coming out of 
Avalon within a matter of days. From there on the Avalon community will 
be leveraging the Merlin platform as the generic framework on which a 
new model-driven solutions will be delivered. I'll try to make sure we 
get release info to you as soon as it becomes available.

Cheers, Steve.


Stephen J. McConnell

Sent via James running under Merlin as an NT service.

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