  Quality requirements typically differ among software features, e.g., due to
different usage contexts of the features, different impacts of related quality
deficiencies onto overall user satisfaction, or long-term plans of the
developing organization. For instance, maintainability requirements might be
particularly high for software features which are frequently used or bear
strategic value for the developing organization. Also, software features where
even the smallest delays are perceived as negative by the user will be
subjected to specially tight performance requirements.
  We defined an operational DSL to define software quality requirements as
individual feature-level constraints based on quantitative measures. The DSL
provides language elements to define the operationalization of measures from
external systems, time series operations, time filters, and the automatic
evaluation of these feature-level constraints in DevOps based on comparison
operators and threshold values. In addition, quality ratings summarize
evaluation results of features on an ordinal grading scheme. Likewise, quality
gates use these quality ratings to reflect the fitness of software features or
the overall software product using different states. Finally, we show an
example based on a widely-adopted secure mobile messaging app that illustrates
the interplay of the different DSL elements.
