  In this paper we show that the long time dynamics (the global attractor) of
the 2D Navier-Stokes equation is embedded in the long time dynamics of an
ordinary differential equation, named {\it determining form}, in a space of
trajectories which is isomorphic to $C^1_b(\bR; \bR^N)$, for $N$ large enough
depending on the physical parameters of the Navier-Stokes equations. We present
a unified approach based on interpolant operators that are induced by any of
the determining parameters for the Navier-Stokes equations, namely, determining
nodal values, Fourier modes, finite volume elements, finite elements, etc...
There are two immediate and interesting consequences of this unified approach.
The first is that the constructed determining form has a Lyapunov function,
thus its solutions converge, as time goes to infinity, to the set of steady
states of the determining form. The second is that these steady states of the
determining form are identified, one-to-one, with the trajectories on the
global attractor of the Navier-Stokes equations. It is worth adding that this
unified approach is general enough that it applies, in an almost
straightforward manner, to a whole class of dissipative dynamical systems.
