Requirements hierarchies should be well defined (e. g., parent / child relationships depending on the level of abstraction of the feature or requirement). Failure to create a hierarchy (such as a tree structure) in turn leads to a two—dimensional trace table of size N x N, where N is the number of requirements associated with traces, and after several thousand requirements, the traces are no longer maintainable or usable. Mitigation techniques include the creation of requirement hierarchies in the database schema that permit database trace queries to return a more meaningful subset of traces.