Natural/Adabas modernization seems to be coming up on our radar a lot these days.
Of course, one option is to modernization/migrate the Natural application and Adabas to Oracle and Java (and get a nice grid play). However, there are some SOA strategies, for accessing both the data and the functional layer if the client chooses to keep their application on the mainframe.
We have several partners that can provide direct access to the data layer and the application layer. Depends on what you want to get to, of course.
So, if you find Natural/Adabas, we can, in fact, interact at several levels.
Building a SOA Environment against Adabas/Natural can be done through a number of options: Integration using one of our validated modernization partners (see http://www.oracle.com/goto/oma), replacing Adabas with Oracle 10g database and porting the Natural application, using a persistency layer such as Oracle TopLink to provide a Natural to Java bridge.