A complementarity framework is described for the modeling of certain c
lasses of mixed continuous/discrete dynamical systems. The use of such
a framework is well known for mechanical systems with inequality cons
traints, but we give a more general formulation which also applies, fo
r instance, to switching control systems, The main theoretical results
in the paper are concerned with uniqueness of smooth continuations; t
he solution of this problem requires the construction of a map from th
e continuous state to the discrete state, A crucial technical tool is
the so-called linear complementarity problem (LCP) from mathematical p
rogramming; we introduce various generalizations of this problem.