  The theory of special relativity can be generalized by means of a new
principle called Conservation of Information. This allows a derivation of the
constancy of the velocity of light with respect to moving frames, and,
consequently, of Einstein's special relativity. The analysis is based on a
review of the concept of observer. It is put forward that observers are not
uniquely defined and that an observational asymmetry, defined by the different
ways in which light influences observations, lies at the origin of the
non-absolutism of time. This observational difference is a kinematic condition,
not an exclusive result for light, implying that non-absolutism of time may
have a cause different from the electromagnetic nature of light. The Lorentz
transformations are rederived and different concepts of the velocity of light,
relative to different classes of observers, are considered.
