  We investigate the class of visibly pushdown languages in the sliding window
model. A sliding window algorithm for a language $L$ receives a stream of
symbols and has to decide at each time step whether the suffix of length $n$
belongs to $L$ or not. The window size $n$ is either a fixed number (in the
fixed-size model) or can be controlled by an adversary in a limited way (in the
variable-size model). The main result of this paper states that for every
visibly pushdown language the space complexity in the variable-size sliding
window model is either constant, logarithmic or linear in the window size. This
extends previous results for regular languages.
