  Software reliability models are an important tool in quality management and
release planning. There is a large number of different models that often
exhibit strengths in different areas. This paper proposes a model that is based
on a geometric sequence (or progression) of the failure rates of faults. This
property of the failure process was observed in practice at Siemens among
others and led to the development of the proposed model. It is described in
detail and evaluated using standard criteria. Most importantly, the model
performs constantly well over several projects in terms of its predictive
validity.
