Permissions for Communities to allow upload of documents, but no further access.

Robin, Can you elaborate your requirement : "but then access needs to be strictly restricted to a limited number of groups, not including the groups that have uploaded the documents."

You want to only Upload the documents but not delete them?

in other words people would submit documents, but not be able to view them via any means from the workflow or documents tab. (in designer view) group A uploads a document that should be viewable by Groups B, C and D from subsequent tasks. the original group A or any other groups other than B C and D should not be able to view edit or download a document

I think it would be better to handle in the Workflow.
Users should be basic users in system and they should not be part of the Designers Group.
Then users would not be able to access the documents from the designer tab.
You cannot handle them through the security for communities as we have only 2 options in security.Administrator or Deny.
If you change the security, then probably user would not be able to upload the documents.

Sorry designer interface, not designer tab

A Shared component may help with this, check out forum.appian.com/.../summary

You create a folder at the start of your process and set its permissions to editor for the first group. Then change permissions to only allow the other groups access to this folder. BTW a normal user being member of the designer group does NOT have permission to any community or folder if not granted explicitely.

Stefan - will this work if this workflow is not coded with SAIL?

Design of this is not bound to SAIL. SAIL is just to define the interface to the user. Creating folders etc. is part of the process model.