Von Neumann’s measurement model in   section 7.1 is often referred to as a “projective measurement”, since its outcome \(k\), see , indicates an earlier quantum property corresponding to the projector \([s^k]\). It is also called a “strong measurement” in contrast to a weak measurement as defined below. In practice one often uses a more general measurement model, referred to as a generalized measurement or POVM (positive operator value measure) where the measurement outcome corresponds not to a specific property but instead to a positive (semi-definite) operator for the measured system at an earlier time.   