Technical debt and waste in non-functional requirements documentation: an exploratory study

Background
It is important to pay attention to non-functional requirements (NFRs). To adequately attend to NFRs, they must be documented - otherwise, developers would not know about their existence. We assume that there exists a positive correlation between the level of importance of an NFR and its documentation.

Aims
The goal is to explore the relationship between the level of importance and degree of documentation for NFRs.

Method
Based on a subset of data acquired from the most recent NaPiRE (Naming the Pain in Requirements Engineering) survey, we calculate for a standard set of NFR types comprising Compatibility, Maintainability, Performance, Portability, Reliability, Safety, Security, and Usability how often respondents state they document a specific type of NFR when they also state that this type of NFR is important. In addition, we calculate the occurrence of potential Technical Debt and Waste.

Results
Our analyses based on 398 survey responses indicate that for four NFR types (Maintainability, Reliability, Usability, and Performance), more than 22% of the 398 survey respondents who labelled those NFR types as important stated that they did not document them. We interpret this as an indication that these NFR types have a higher risk of Technical Debt than other NFR types. Regarding Waste, the problem is less frequent, with the exception of Security with 15% of respondents stating that they document requirements which they do not consider important.

Conclusions
There is a clear indication that for a fixed set of NFRs lack of documentation of important NFRs occurs often, suggesting a risk of Technical Debt. The potential risk of incurring Waste is also present but to a lesser extent.