Gray links in the use of requirements traceability

The value of traceability is in its use. How do different software engineering tasks affect the tracing of the same requirement? In this paper, we answer the question via an empirical study where we explicitly assign the participants into 3 trace-usage groups of one requirement: finding its implementation for verification and validation purpose, changing it within the original software system, and reusing it toward another application. The results uncover what we call "gray links"--around 20% of the total traces are voted to be true links with respect to only one task but not the others. We provide a mechanism to identify such gray links and discuss how they can be leveraged to advance the research and practice of value-based requirements traceability.