  The growing complexity of software systems and the influence of
software-supported decisions in our society awoke the need for software that is
transparent, accountable, and trustworthy. Explainability has been identified
as a means to achieve these qualities. It is recognized as an emerging
non-functional requirement (NFR) that has a significant impact on system
quality. However, in order to incorporate this NFR into systems, we need to
understand what explainability means from a software engineering perspective
and how it impacts other quality aspects in a system. This allows for an early
analysis of the benefits and possible design issues that arise from
interrelationships between different quality aspects. Nevertheless,
explainability is currently under-researched in the domain of requirements
engineering and there is a lack of conceptual models and knowledge catalogues
that support the requirements engineering process and system design. In this
work, we bridge this gap by proposing a definition, a model, and a catalogue
for explainability. They illustrate how explainability interacts with other
quality aspects and how it may impact various quality dimensions of a system.
To this end, we conducted an interdisciplinary Systematic Literature Review and
validated our findings with experts in workshops.
