Oracle BPM 11g (or BPEL)  uses XML to pass along process payload information.  To modify this information in a UI, BPM data controls are typically used to update this data from the ADF user interface. This is a well known technique and easy to do.  These data controls can be generated from the human task UI wizard or through the new gallery's "ADF Task Flow Based on Human Task", Figure 1.  So long as the UI uses the BPM's data controls, all is well.