Relational Quantum Measurements, Information and State Collapse

The quantum measurement problem considered for measuring system (MS) consist of measured state S (particle), detector D and information processing device (observer) O. It's shown that O states selfreference structure results in principal nonobservability of MS interference terms which discriminate pure and mixed S states. Such observables restriction permit to construct for MS states subjective representation (SR) which describes probabilistic evolution for measurement events observed by $O$ and his subjective information about S values. SR is dual and nonequivalent to MS Hilbert space $H$ for external observer $O'$. Due to it SR evolution is compatible with Schrodinger linear MS evolution observed by $O'$. It's argued that SR evolution corresponds to S state collapse for individual events observed by $O$.