This paper develops a generalized definition of the observer as a "constraint-mediated coherence-reduction function" rather than as a conscious subject or measuring apparatus alone. In simple terms, the observer reduces possibility into the discrete. This is operative across all scale and is not at all limited by entities or instrumentation, though they too are expressions of the Observer Function. In this formulation, observer function occurs wherever a boundary, gradient, constraint, apparatus, field, or system reduces a more open coherent condition into distinction, localization, information, or closure.
Philip Lilien (Sat,) studied this question.