Need hints on distributed DB

Hi,

I'll soon run in a probaply pretty common problem with 2 site
replication. Basically it's a "central server and off-line sales person"
problem.

We currently hold our customer and business' data in one server. Soon
we'll get another site which basically will work on a regional separate
project. While the set of potential costomers that overlap will be
limited, there still will be customers that are related to both sites.

The new site will only mind operational acquisition stuff and project
related PR. Billing will be on the main site.

While doing that, the 2nd site will report incoming orders to the main
site and of course there will be additions and changes to shared
costomer records - like adresses, contact person, phone numbers - that
have to be synchronized both ways.

There is no online-connection planned. The synchronisation should be
made via filed queries that extract the changed recorddata that'll be
transfered perhaps by email or via ssh remote login.

How could I identify, ex- and import such changed data ?
Maybe there are concurrent changes to be catched ? Like site1 changes
field1 and site2 field2 of the same record.

The whole point is to share as much data as possible so both sites
profit on additions or corrections.

Any pointer to documentation in that matter would be appreciated.
Everthing is appreciated.
Currently we are using ms-access as front- & backend. I'm planning to
move the backend to something more appropriate like postgresql.

regards ... Andreas