Begin with DSL for the example

ros2rag.example/src/main/jastadd/Example.ros2rag

+/**
+ * Version 2020-04-17
+ */
+// --- update definitions ---
+read Joint.CurrentPosition using LinkStateToIntPosition ;
+write RobotArm._AppropriateSpeed using CreateSpeedMessage ;
+
+// --- dependency definitions ---
+RobotArm._AppropriateSpeed canDependOn Joint.CurrentPosition as dependency1 ;
+
+// --- mapping definitions ---
+LinkStateToIntPosition: map protobuf panda.Linkstate.PandaLinkState x to IntPosition y {
+  panda.Linkstate.PandaLinkState.Position p = x.getPos();
+  y = IntPosition.of((int) p.getPositionX(), (int) p.getPositionY(), (int) p.getPositionZ());
+}
+
+CreateSpeedMessage: map double x to protobuf config.Robotconfig.RobotConfig y {
+  y = config.Robotconfig.RobotConfig.newBuilder()
+    .setSpeed(x)
+    .build();
+}