The user is to be assesed by a property such as:

• Age
• PostCode/Zip
• Membership History
• ...

The realm is a string that's defined to identifying that property, such as:

• 'age'
• 'postcode'
• 'membership_duration'

A condition of a realm.

For example, if realm was 'age' then grant IDs might be:

• is over 18
• is between 20 - 30
• is under 75

More than one grant ID can be defined per realm.

Each grant ID can control view, edit and delete options for a node.