  [Context] Quality requirements are important for product success yet often
handled poorly. The problems with scope decision lead to delayed handling and
an unbalanced scope. [Objective] This study characterizes the scope decision
process to understand influencing factors and properties affecting the scope
decision of quality requirements. [Method] We studied one company's scope
decision process over a period of five years. We analyzed the decisions
artifacts and interviewed experienced engineers involved in the scope decision
process. [Results] Features addressing quality aspects explicitly are a minor
part (4.41%) of all features handled. The phase of the product line seems to
influence the prevalence and acceptance rate of quality features. Lastly,
relying on external stakeholders and upfront analysis seems to lead to long
lead-times and an insufficient quality requirements scope. [Conclusions] There
is a need to make quality mode explicit in the scope decision process. We
propose a scope decision process at a strategic level and a tactical level. The
former to address long-term planning and the latter to cater for a speedy
process. Furthermore, we believe it is key to balance the stakeholder input
with feedback from usage and market in a more direct way than through a long
plan-driven process.
