  We give a semantics to iterated update by a preference relation on possible
developments. An iterated update is a sequence of formulas, giving (incomplete)
information about successive states of the world. A development is a sequence
of models, describing a possible trajectory through time. We assume a principle
of inertia and prefer those developments, which are compatible with the
information, and avoid unnecessary changes. The logical properties of the
updates defined in this way are considered, and a representation result is
proved.
