In order for a mobile robot to accomplish a non-trivial task, the task must be described in terms of primitive actions of the robot's actuators. Our contention is that the transformation from the high level description of the task to the primitive actions should be performed primarily at execution time, when knowledge about the environment can be obtained through sensors. Our theory is based on the premise that proper application of knowledge increases the robustness of plan execution. We propose to produce the detailed plan of primitive actions and execute it by using primitive components that contain domain specific knowledge and knowledge about the available sensors and actuators. These primitives perform signal and control processing as well as serve as an interface to high-level planning processes. In this work, importance is placed on determining what information is relevant to achieve the goal as well as determining the details necessary to utilize the sensors and actuators.