 What should this actualization rule look like? In the mid-1990s a series of authors confronted this question (Clifton 1995a, 1995b, Dickson 1995a, 1995b). These authors proposed conditions to be satisfied by an actualization rule that defines a set of possibilities purely from the dynamical state, and concluded that the possible value states of the components of a two-part composite system should be given by the states occurring in the Schmidt (bi-orthogonal) decomposition of the dynamical state, or, equivalently, by the projectors occurring in the spectral decomposition of the density matrices representing partial systems (obtained by partial tracing) —see Section 4 for details.