Many techniques have been developed to help programmers locate source code that corresponds to specific functionality, i.e., concern or feature location, as it is a frequent software maintenance activity. This paper proposes operational definitions for differentiating the roles that each program element of a concern plays with respect to the concerns implementation. By identifying the respective roles, we enable evaluations that provide more insight into comparative performance of concern location techniques. To provide definitions that are specific enough to be useful in practice, we focus on the subset of concerns that are action-oriented. We also conducted a case study that compares concern mappings derived from our role definitions with three developers mappings across three concerns. The results suggest that our definitions capture the majority of developer-identified elements and that control-flow islands (i.e., groups of elements with little to no control flow connections) can cause developers to omit relevant elements.