Advanced Concepts. Advanced concepts developed in the context of the client library are documented separately. In general, these concepts are developed for the standard rclcpp first, before implementing a tailored C version. These are: • Real-Time Executor • System Modes 5 Annex 2: Decision paper Content of from 11th December 2020. This document served as decision template for the design and implementation of the micro-ROS client library in March 2019. We discuss different options and existing starting points for this un- dertaking, decision criteria and analysis results regarding the existing assets.