Administrator can do everything.
User1 can put files and create subfolders inside User1 Folder. User1 can open it and read it but cannot modify it and delete it.
User2 has the similar security needs.
Folder structure:
User1 Folder's properties:
When user1 logs on, he can put files inside the companyFile/User1 folder. But he cannot delete and modify them.Write Attributes and Write Extended Attributes control the modification. If you assign both Write attributes and Write Extended attributes to user1, user1 can modify the files.
