  User eXperience (UX) is becoming increasingly important for success of
software products. Yet, many companies still face various challenges in their
work with UX. Part of these challenges relate to inadequate knowledge and
awareness of UX and that current UX models are commonly not practical nor well
integrated into existing Software Engineering (SE) models and concepts.
Therefore, we present a conceptual UX-aware model of requirements for software
development practitioners. This layered model shows the interrelation between
UX and functional and quality requirements. The model is developed based on
current models of UX and software quality characteristics. Through the model we
highlight the main differences between various requirement types in particular
essentially subjective and accidentally subjective quality requirements. We
also present the result of an initial validation of the model through
interviews with 12 practitioners and researchers. Our results show that the
model can raise practitioners' knowledge and awareness of UX in particular in
relation to requirement and testing activities. It can also facilitate
UX-related communication among stakeholders with different backgrounds.
