DBI is the interface your Perl program uses to the high-level database routines. Those routines in turn call the low-level backend routines that are database specific.

One of these backend routines is ODBC, which itself is an indirection layer to let many databases have a similar API.

So it'd go yourcode -to- DBI -to- DBD::ODBC -to- random back end

Sure, you can certainly talk directly to ODBC, but then you'd lose the option to go with a non-ODBC backend by changing just a few lines of code, such as mysql via: yourcode -to- DBI -to- DBD::mysql -to- mysql API.

So, ODBC doesn't replace DBI. DBI doesn't replace ODBC. They're indirections at different levels.

-- Randal L. Schwartz, Perl hacker