We were recently working on designing a moderately complicated permissions system, and my impression is that it's impossible to create such a general-purpose en

We were recently working on designing a moderately complicated permissions system, and my impression is that it's impossible to create such a general-purpose engine and gem that covers enough of the cases that you'll have to manage, without creating something that is incredibly complicated to set up and manage. Except for a few standardized domains, you'll always have rules that are easier to express and maintain with some custom, domain-specific code.