Extensible CMS Framework

Hi all,

We are currently evaluating existing content management solutions. One 
of our primary concerns (among our list of requirements) is that we want 
to leverage existing technologies that have been engineered in house. 
For example we would like to leverage the existing source control and 
staging system that we have built with TLA rather than switch our source 
control over to some arbitrary source control that is build into the CMS 
we choose. Through the research process I've come to realize that what 
I'm really looking for is an extensible working CMS that serves as a 
framework which manages the interactions between CMS components (e.g. 
document work flow, access control, source control, i18n, publishing, 
etc...) and allows us to plug in our own code where we want to take over 
control of a CMS task (e.g. source control). For an example of this 
style of application see Eclipse 
(http://www.eclipse.org/org/index.html). Is there anything like this out 
there? We'd like to find something in either PHP or Java since we have 
developers who are experts in those languages, but this is only a 
preference. If you need anymore information (additional requirements, 
etc...) please let me know.

Thanks in advance for your responses!

Kind Regards,
Darryl Kuhn