Have a look at the documentation: http://docs.oracle.com/cd/E23943_01/dev.1111/e10224/bp_workflow.htm
Also, there are some examples on internet.
You can use the TaskService to connect on behalf a user and finish the task with an outcome.
Luis F Heckler
But if you are talking about define the outcomes dynamically at runtime, as far as I know this is not possible.
If you really need this you can setup generic outcomes (outcome1, outcome2, etc) and dynamically set the button label at the ADF form, but this is not a best practice in terms of business process modelling.