Backup database and logs

Hi all,
I want to take a backup of the database and the transaction logs of
the postgresql data. I am using postgresql 7.4.6. I would be happy if
any of u can answer the following questions..
1. Is there a way to do an incremental backup? I did a search in
google only to find that it is due in
7.3.(http://archives.postgresql.org/pgsql-admin/2002-07/msg00367.php)
Is it already been implemented? If so, how to use that?
2. How to backup the data using a sql query? I found that the db can
be backed-up using pg_dump or by doing a copy of the db directory. I
would like to do that from a SQL query instead, like the BACKUP query
of MS SQL Server.
3. Is there a way to backup the transaction logs? Does backing up the
log file solve the problem?

Thanks a lot!
Prasanna.