Linear types provide the framework for a safe embedding of mutable state in functional languages by enforcing the principle that variables of linear type must be used exactly once. A potential disadvantage of this approach is that it places read accesses to such variables under the same restriction as write accesses, and thus prevents reads to proceed in parallel. We present here an extension o...

We attempt to dissolve the measurement problem using a quasi-anthropic principle which allows us to invoke rational observers. We argue that the key feature of such observers is that they are rational (we need not care whether they are ‘classical’ or ‘macroscopic’ for example) and thus, since quantum theory can be expressed as a rational theory of probabilistic inference, the measurement proble...

The concept of`measurement' becomes so fuzzy on reeection that it is quite surprising to have it appearing in physical theory at the most fundamental level.. .. D]oes not any analysis of measurement require concepts more fundamental than measurement? And should not the fundamental theory be about these more fundamental concepts? (Bell 1981 1, page 117])

In this paper, we explore the connection between the classic, input output based theory of observers for linear functions of the state and the theory of behavior based observers as developed in the paper Valcher and Willems [1999].