  We apply a compositional formal modeling and verification method to an
autonomous aircraft taxi system. We provide insights into the modeling approach
and we identify several research areas where further development is needed.
Specifically, we identify the following needs: (1) semantics of composition of
viewpoints expressed in different specification languages, and tools to reason
about heterogeneous declarative models; (2) libraries of formal models for
autonomous systems to speed up modeling and enable efficient reasoning; (3)
methods to lift verification results generated by automated reasoning tools to
the specification level; (4) probabilistic contract frameworks to reason about
imperfect implementations; (5) standard high-level functional architectures for
autonomous systems; and (6) a theory of higher-order contracts. We believe that
addressing these research needs, among others, could improve the adoption of
formal methods in the design of autonomous systems including learning-enabled
systems, and increase confidence in their safe operations.
