  Background: Requirements Engineering is crucial for project success, and to
this end, many measures for quality assurance of the software requirements
specification (SRS) have been proposed. Goal: However, we still need an
empirical understanding on the extent to which SRS are created and used in
practice, as well as the degree to which the quality of an SRS matters to
subsequent development activities. Method: We studied the relevance of SRS by
relying on survey research and explored the impact of quality defects in SRS by
relying on a controlled experiment. Results: Our results suggest that the
relevance of SRS quality depends both on particular project characteristics and
what is considered as a quality defect; for instance, the domain of safety
critical systems seems to motivate for an intense usage of SRS as a means for
communication whereas defects hampering the pragmatic quality do not seem to be
as relevant as initially thought. Conclusion: Efficient and effective quality
assurance measures must be specific for carefully characterized contexts and
carefully select defect classes.
