To study einselection, an operational definition of pointer states has been introduced. This is the "predictability sieve" criterion, based on an intuitive idea: Pointer states can be defined as the ones which become minimally entangled with the environment in the course of their evolution. The predictability sieve criterion is a way to quantify this idea by using the following algorithmic procedure: For every initial pure state | ψ ψ ⟩ ⟩ , one measures the entanglement generated dynamically between the system and the environment by computing the entropy: