Refining high-level requirements into low-level ones is a common task, especially in safety-critical systems engineering. The objective is to describe every important aspect of the high-level requirement in a low-level requirement, ensuring a complete and correct implementation of the system's features. To this end, standards and regulations for safety-critical systems require reviewing the coverage of high-level requirements by all its low-level requirements to ensure no missing aspects.

Software engineers use requirement-to-method trace matrices to indicate the methods implementing different system requirements. Requirement-to-method trace matrices pinpoint the exact method implementing each requirement, which facilitates software maintenance and bug fixing. The code structure of a system can be used to make predictions about requirement-to-method traces. In this paper, we present a data set documenting the requirement-to-method traces as well as the code structure (methods, variables, etc.) for four open source systems. The code structure was obtained by parsing the systems under consideration and extracting the methods, variables, etc. The requirement-to-method trace matrices were obtained by resorting to students as well as to the original developers of the systems who provided us with the list of requirement-to-method traces.