Relational quantum mechanics

I suggest, that the common unease with taking quantum mechanics as a fundamental description of nature (the ''measurement problem'') could derive from the use of an incorrect notion, as the unease with the Lorentz transformations before Einstein derived from the notion of observer-independent time. I suggest that this incorrect notion that generates the unease with quantum mechanics is the notion of ''observer-independent state'' of a system, or ''observer-independent values of physical quantities.'' I reformulate the problem of the ''interpretation of quantum mechanics'' as the problem of deriving the formalism from a set of simple physical postulates. I consider a reformulation of quantum mechanics in terms of information theory. All systems are assumed to be equivalent, there is no observer-observed distinction, and the theory describes only the information that systems have about each other; nevertheless, the theory is complete.