This homepage contains some information about a concept of synchronizing Databases I called "Teamworking Databases" back in 1994.
There is also a sample AppleScript program to synchronize two FileMaker databases, called FileMerger. Note that this Script is a working prototype, but not a finalized tool. It is (due to AppleScript) VERY slow - however, it can still be very useful.
When two databases are maintained separatley (not on the same LAN/WAN) for a while, the problem of re-synchronizing appears, to update both databases later. This is not exceptionally complicated, but is not a simple export/import operation either. Synchronisation must be done on a record by record basis (field by field would be even better), controlled by modification dates.
Back in 1994, when I wrote an USENET article on that topic, there was no PC software available at all to do this sort of thing. I tried to suggest to CLARIS in an email message to add this simple, yet extremely useful feature to FileMaker (but didn't get an answer ever).
So I wrote an Applescript (mentioned above, named "FileMerger", which was able to do (very slowly, and with user interface restrictions) what I'd been hoping to see in a future version of FileMaker's "Import" command.
Today, the concept is more or less implemented in those specialized
synchronizing tools for PDAs (Newton [RIP], PalmPilot, etc.).
However, Filemaker still lacks any synchronisation feature....