  An approach is developed which enables one to analyze gravitational effects
without usage of any concrete model of geometry (or a class of models of
geometry) of space-time and even without any coordinate system. Instead, the
formalism of the group of paths is used. An element of this group (a class of
curves in Minkowski space) is associated with each curve in the curved
space-time and called its `flat model'. The analysis of observational data in
terms of flat models of closed curves is interpreted as a formalization of the
analysis which a `naive observer' (knowing nothing about the space-time being
curved) applies to his observations.
