§2.1.2.(b) No cycles

The base class mentioned after playedBy may not be an enclosing type (at any depth) of the role class being defined.
This rule prohibits the creation of cycles where the base instance of a given role R contains roles of the same type R.
More generally any sequence of classes C1, C2, .. Cn were each Ci+1 is either a member or the base class of Ci and Cn = C1 is forbidden.
Conversely, it is also prohibited to bind a role class to its own inner class.