  I describe a constructive foundation for Quantum Mechanics, based on the
discreteness of the degrees of freedom of quantum objects and on the Principle
of Relativity. Taking Einstein's historical construction of Special Relativity
as a model, the construction is carried out in close contact with a simple
quantum mechanical Gedanken experiment. This leads to the standard axioms of
Quantum Mechanics. The quantum mechanical description is identified as a tool
that allows describing objects with discrete degrees of freedom in space-time
covariant with respect to coordinate transformations. An inherent property of
this description is a quantum mechanical interaction mechanism. The
construction gives detailed answers to controversial questions, such as the
measurement problem, the informational content of the wave function, and the
completeness of Quantum Mechanics.
