Viewer: read only. User: edit items, adjust stock, check out, edit BOMs and categories. Admin: everything, including deleting items and categories and managing users. Users and admins can also be given duties, which say whose turn a request is: Approver approves or rejects requests, and gets an email for each new one. Purchaser places orders and manages jobs, vendors and payment methods, and gets an email when an order is approved. Admins can approve and purchase without the ticks, as a backup, but get those emails only if ticked. Changes apply straight away.