The MechatronicUML Requirements Engineering Method: Process and Language In this technical report, we present the MechatronicUML requirements engineering method. The method encompasses a process and a scenario-based modeling language for the documentation and analysis of requirements on the message-based interaction behavior of software-intensive systems. The modeling language uses a scenario notation based on Modal Sequence Diagrams (MSDs), which borrows concepts of UML Interactions as well as of Live Sequence Charts. Furthermore, we introduce the so-called Emergency Braking & Evasion System (EBEAS) as a running example, which is based on current and upcoming real-world driver assistance systems.