 In spite of the fact that this modal interpretation is characterized by the central role played by biorthogonal decomposition, two different versions can be distinguished. One of them adopts a metaphysics in which all properties are relational and, as a consequence, the fact that the application of the interpretation is restricted to subsystems of a two-component compound system is not a problem (Kochen 1985). This relation has been called “witnessing”: properties are not possessed by the system absolutely, but only when it is “witnessed” by another system. Consider the measurement described above: the pointer “witnesses” the value acquired by the measured observable of the measured system.