  Context. Own experiences and faulty decisions can be an important source of
information for software architects. The experiences and mistakes of other
architects can also be valuable information sources. Goal. Under the assumption
that the knowledge about faulty decisions, i.e., mistakes, regarding software
architecture is not shared adequately in practice, this work qualitatively
investigates the handling and particularly communication of those mistakes by
software architects. Method. We conducted a grounded-theory study in which we
interviewed ten German software architects from various domains. Results. We
identified software architects' definitions of architectural mistakes, their
handling of these mistakes, and their preferred communication strategies
regarding these mistakes. We found that architects communicate mistakes mainly
within their project teams and seldom within or across companies. Conclusions.
We derived strategies to make learning and prevention of mistakes more
effective. To share experiences and knowledge beyond architects' peer groups,
companies should invest more effort in discussing mistakes more consciously and
create an environment where mistakes can be discussed openly.
