Groupmode and currentgroup setters will allow overriding the activity settings programtically.
In a group peer review activity the submission activity may be in a separate group mode. The review activity needs to show the reviewing group the submission of the reviewed group. That submission can be populated to the entry of the reviewing group via the dataformview field. However, since the submission activity is set to separate groups, the review team will not have access to the reviewed submission and will not be able to see it.
Now, with the groupmode and currentgroup setters, the dataformview field can override the group settings of the target dataform to the effect that access to the designated entry will be allowed.