  We present a general setting for structure-sequence comparison in a large
class of RNA structures that unifies and generalizes a number of recent works
on specific families on structures. Our approach is based on tree decomposition
of structures and gives rises to a general parameterized algorithm, where the
exponential part of the complexity depends on the family of structures. For
each of the previously studied families, our algorithm has the same complexity
as the specific algorithm that had been given before.
