In the Siebel Object Type Business Component Field
has attribute named
Predefault Value
you can provide Siebel valid expression to populate value when creating new record using expression
Field: 'Id'
or
Expr: 'RowIdToRowIdNum ([Id])'.
Alternatively you can also write Server side script on
Siebel Object Type Business Component
in the method
BusComp_PreNewRecord
to populate customized value when creating new record.
Alternatively you can also use
Database Trigger
which can also populate customized value to columns and will be available in Business Component Field value.