  We present a Riemann-Hilbert problem formalism for the initial-boundary value
problem for the Sasa-Satsuma(SS) equation on the finite interval. Assume that
the solution existes, we show that this solution can be expressed in terms of
the solution of a $3\times 3$ Riemann-Hilbert problem. The relevant jump
matrices are explicitly given in terms of the three matrix-value spectral
functions $s(k)$, $S(k)$ and $S_L(k)$, which in turn are defined in terms of
the initial values, boundary values at $x=0$ and boundary values at $x=L$,
respectively. However, for a well-posed problem, only part of the boundary
values can be prescribed, the remaining boundary data cannot be independently
specified, but are determined by the so-called global relation. Here, we
analyze the global relation to characterize the unknown boundary values in
terms of the given initial and boundary data.
