Spring security in grails - roles and permissions

There is nice plugin for using Spring security in Grails - it integrates nicely in application, can be heavily customized and is easy to use. I didn't had extensive experience with Spring security before, but all security frameworks that I used, have something that represents roles and permissions. Role is group of permissions, and permissions are either defined only for groups or can be assigned to users explicitly. From first glance at Spring security there is only concept for roles (or as they called in plugin - Authorities). It confused me very much and created impression of very basic framework.

It took some time to figure out, that on the contrary - Spring security is very powerful and flexible also in this sense. Basically, all it cares is what authorities you return in your users getAuthorities() method. So you can generate whatever hierarchy of permissions you want, possibly adjust it by the time or the day, or simply generate it on the fly.