Sage ships with an ODBC driver that can be used to provide read-only access to the underlying data tables in Sage, the SDO (Sage Data Objects) can provide read-write access to these tables, but often, it's hard to know which field you need to edit. Therefore this ODBC driver can come in handy listing tables, columns, and hints for what each field is for.
After the installation of sage, a DSN should be setup, if you go to Start Contol Panel Administrative Tools ODBC Manager, then select "System DSN", you should see a DSN called, "SageLine50v9" or similar.
If you download a free utility called DSN2CSV here http://bitdaddys.com/dsn2csv.html
and, from the command prompt type:
dsn2csv "SageLine50v9" * "Manager" ""
A sample schema from Line 50 version 9 can be found here: