 It is not possible to derive any necessary qualities of computational systems and data domains beyond the fact that they are general mathematical operations and structures. Data domains on which Turing equivalent systems are defined are not necessarily physical, nor temporal, nor spatial, not binary or digital. At any moment a new member for the class can be introduced. We know that there are computational systems that are weaker than the class of Turing machines (e.g., regular languages). We cannot rule out the possibility that one-day we come across a system that is stronger. The thesis that such a system does not exist is known as the Church-Turing thesis (see entry on  Church-Turing thesis):