Multiple SQL statements within a function...

If you have multiple SQL statements within a single SQL or PL/PGSQL
function, are they automatically treated as a single multi-statement
transaction or does this require you to put BEGIN/COMMIT statements within
your function which itself would require you to be cognoscente of the
transactional state of your current database session.

Am assume the MST is implicit but have been looking for answer in online
docs and have  been unable to confirm one way or the other.  Can anyone
sight a documentation reference?

Thanks,

Marc Mitchell
Enterprise Information Solutions, Inc.
marcm@eisolution.com