Title: "A quantum theory for a total system including a measuring apparatus"

We propose a quantum theory for a total system composed of a measuring apparatus and an environment, where the measuring apparatus also plays the role of a reference system (RS). The theory is an extension of the standard formalism of quantum mechanics, with the following additional assumptions: (i) A RS has some definite properties in its own frame of reference and (ii) under certain condition a system can be employed as a RS. In this theory, collapse of state vector is not a dynamical process, but is a phenomenon due to the possibility of more than one physically equivalent descriptions.