  Over recent decades, scenarios and scenario-based software/system engineering
have been actively employed as essential tools to handle intricate problems,
validate requirements, and support stakeholders' communication. However,
despite the widespread use of scenarios, there have been several challenges for
engineers to more willingly utilize scenario-based engineering approaches
(i.e., scenario methods) in their projects. First, the term scenario has
numerous published definitions, thus lacking in a well-established shared
understanding of scenarios and scenario methods. Second, the conceptual basis
for engineers developing or employing scenarios is missing. To establish shared
understanding and to find common denominators of scenario methods, this study
leverages well-defined metamodeling and conceptualization that systematically
investigate the concepts under analysis and define core entities and their
relations. By conducting a semi-systematic literature review, conceptual
variables are collected and conceptualized as a conceptual meta-model. As a
result, this study introduces scenario variables (SVs) that represent
constructs/semantics of scenario descriptions, according to 4 levels of
constructs of a scenario method. To evaluate the comprehensibility and
applicability of the defined variables, we analyze five existing scenario
methods and their instances in automated driving system (ADS) domains. The
results showed that our conceptual model and its constituent scenario variables
adequately support the understanding of a scenario method and provide a means
for comparative analysis between different scenario methods.
