This book treats various aspects of the quantum theory of measurement,
partially in a relativistic framework. Measurement(-like) processes in
quantum theory are identified and analysed; and the quantum operator
formalism is derived in full generality without postulating operators as
observables. Consistency conditions are derived, expressing the
requirement of Lorentz-frame independence of outcomes of spacelike
separated measurements and implying the impossibility of using quantum
nonlocality to send signals faster than light. Local commutativity is
scrutinized. The localization problem of relativistic quantum theory is
studied, including comprehensive derivation of the theorems of
Hegerfeld, Malament and Reeh-Schlieder. Finally, the quantum formalism
is derived from the dynamics of particles with definite positions in
Bohmian mechanics.