  In later models, GRW proposed to interpret the quantum state as a density of mass and they postulated that if almost all the density of mass of a system is concentrated in a certain region, then the system is located in that region. Accordingly, pointers of measurement apparatuses do have definite positions at the end of measurement interactions. Yet, this solution has also given rise to a debate (see Albert and Loewer 1995, Lewis 1997, 2003a, 2004, Ghirardi and Bassi 1999, Bassi and Ghirardi 1999, 2001, Clifton and Monton 1999, 2000, Frigg 2003, and Parker 2003).