Distributed models

Hello,
I am designing a web application that has several tiers including a
Flex
client, Rails server and SAP back-end. The application is an extension
of
functionality offered by SAP system. SOAP services are used
communicate with
the back-end.
I am pondering on the implications of the fact that some of my data
models
are likely to be in the back-end and some in the Rails application and
some
are distributed (shared) between Rails and the back-end. I would
appreciate
any pointers toward relevant knowledge on this subject and if anyone
tried
something similar with Rails.
Some of the questions I have to find answers to are:

  • How does one use ActiveRecord with shared models?
  • What are the implications of this type of distributed design?
  • Relevant design patterns.

thank you,
Slava