  [Context&Motivation]Due to the managerial ,operational and evolutionary
independence of constituent systems (CSs) in a System of Systems (SoS) context,
top-down and linear requirements engineering (RE) approaches are insufficient.
RE techniques for SoS must support iterating, changing, synchronizing, and
communicating requirements across different abstraction and hierarchy levels as
well as scopes of responsibility. [Question/Problem] We address the challenge
of SoS requirements specification, where requirements can describe the SoS
behavior, but also the behavior of CSs that are developed independently.
[Principal Ideas] To support the requirements specification in an SoS
environment, we propose a scenario-based and iterative specification technique.
This allows requirements engineers to continuously model and jointly execute
and test the system behavior for the SoS and the CS in order to detect
contradictions in the requirement specifications at an early stage.
[Contribution] In this paper, we describe an extension for the
scenario-modeling language for Kotlin (SMLK) to continuously and formally model
requirements on SoS and CS level. To support the iterative requirements
specification and modeling we combine SMLK with agile development techniques.
We demonstrate the applicability of our approach with the help of an example
from the field of e-mobility.
