Diagram illustrating the required tracing between certification artifacts, as required by the RTCA DO-178C standard. Thin blue-colored traces and blue-filled boxes are required only for Level A.  Purple-colored traces and purple-filled boxes are required for Levels A, B, and C. Thick green-colored traces and green-filled boxes are for Levels A, B, C, and D.  Level E does not require any tracing. The references on each trace arrow represent references to the standard for the objective, the activity, and the review/verification, respectively.
<a href="//commons.wikimedia.org/wiki/User:Svleest" title="User:Svleest">Steven H. VanderLeest</a>
<span class="int-own-work" lang="en">Own work</span>