Is it possible to call Oracle functions from Webfocus? If so, what method should I use?

Thanks

You can invoke Oracle stored procedures, whith some limitations described in the "iWay data administration manual ..." (v. 5.2, chapter 27. "Getting Started in Oracle"). There is also an example of the syntax.
IBI Tech Support link

If you would like to call the Oracle function (PL/SQL: CREATE FUNCTION), you can wrap the function within a PL/SQL procedure and then call it using SQL PASSTHROUGH from FOCUS.