I would say what they call 'composition by capability' is a theory of categorization, in fact similar to Wittgenstein's family resemblance theory.

That said, it's not obvious that the underlying data model needs or should map to a theoretical model for how human cognition works. Maybe it should and it's worth considering the theoretical landscape before setting out, but there are other features that come into play.

I know very little about library science, but I assume they take a more practical (for this task) approach to this that's worth looking into.

You should definitely look into it, especially if you like pedantic arguments.