  Requirements Engineering (RE) has established itself as a software
engineering discipline during the past decades. While researchers have been
investigating the RE discipline with a plethora of empirical studies, attempts
to systematically derive an empirically-based theory in context of the RE
discipline have just recently been started. However, such a theory is needed if
we are to define and motivate guidance in performing high quality RE research
and practice. We aim at providing an empirical and valid foundation for a
theory of RE, which helps software engineers establish effective and efficient
RE processes. We designed a survey instrument and theory that has now been
replicated in 10 countries world-wide. We evaluate the propositions of the
theory with bootstrapped confidence intervals and derive potential explanations
for the propositions. We report on the underlying theory and the full results
obtained from the replication studies with participants from 228 organisations.
Our results represent a substantial step forward towards developing an
empirically-based theory of RE giving insights into current practices with RE
processes. The results reveal, for example, that there are no strong
differences between organisations in different countries and regions, that
interviews, facilitated meetings and prototyping are the most used elicitation
techniques, that requirements are often documented textually, that traces
between requirements and code or design documents is common, requirements
specifications themselves are rarely changed and that requirements engineering
(process) improvement endeavours are mostly intrinsically motivated. Our study
establishes a theory that can be used as starting point for many further
studies for more detailed investigations. Practitioners can use the results as
theory-supported guidance on selecting suitable RE methods and techniques.
