  Functional dependencies and feature interactions in automotive software
systems are a major source of erroneous and deficient behavior. To overcome
these problems, many approaches exist that focus on modeling these functional
dependencies in early stages of system design. However, there are only few
empirical studies that report on the extent of such dependencies in industrial
software systems and how they are considered in an industrial development
context. In this paper, we analyze the functional architecture of a real
automotive software system with the aim to assess the extent, awareness and
importance of interactions between features of a future vehicle. Our results
show that within the functional architecture at least 85% of the analyzed
vehicle features depend on each other. They furthermore show that the
developers are not aware of a large number of these dependencies when they are
modeled solely on an architectural level. Therefore, the developers mention the
need for a more precise specification of feature interactions, e.g., for the
execution of comprehensive impact analyses. These results challenge the current
development methods and emphasize the need for an extensive modeling of
features and their dependencies in requirements engineering.
