A wiki can have the following access policy:

• Public. Anyone can access and edit pages. That means it isn't necessary to register or login to access or edit pages. A default Anonymous user is assume to be logged if the user doesn't logged.
• Public Access. Anyone can access pages but need to be logged before editing pages.
• Private. Only logged users can access and edit pages.
• PrivateExplicit: Private Explicit (only registered users with Explicit permissions can view and edit pages)