On the Node Properties documentation

[mathiasekstedt]

• Clarify what the difference is for Viability and Traversability
• Explain Compromised first
• Clarify that Necessity is "looking forward"

[kasanari]

I will add that the text about exist steps is confusing to me.

if an exist step has any of its requirements met it is viable. It will be unviable if none of its requirements are present.

if a notExist step has any of its requirements met it is not viable. It will be viable if none of its requirements are present.

This makes it sound like exist and OR are equivalent.
In the code, neither exist or notExist checks anything but it's own existance_status (which in itself is a weird concept but I assume it comes from wanting to specify that certain attack steps can never be done for no good reason).

        case 'exist':
            assert isinstance(node.existence_status, bool), \
                f'Existence status not defined for {node.full_name}.'
            return not node.existence_status
        case 'notExist':
            assert isinstance(node.existence_status, bool), \
                f'Existence status not defined for {node.full_name}.'
            return bool(node.existence_status)