## 4 Results and Discussion
### RQ2: In Which RE Activities Have the CVs Been Reported? In order to provide meaningful answers to this RQ, we mapped the RE activities reported in the primary studies to those proposed in [6]: Elicitation, Specification, Analysis, Validation, \begin{table}
\begin{tabular}{l c c} \hline \hline
**Primary Paper** & **Type of CV** & **Support Level** \\ \hline S1, S2, S3, S4, S5, S8, S9, S10, S11, S12, S15, S16, S17, S18, S19, S22, S23, & \\ S24, S25, S27, S28, S29, S30, S31, S32, S33, S34, S35, S36, S37, S38, S40, S41, & \\ S42, S43, S44, S45, S46, S47, S48, S51, S52, S53, S54, S55, S56, S57, S58, & Ontology & 79 \\ S60, S61, S62, S63, S64, S65, S66, S67, S68, S69, S70, S71, S72, S73, S74, & \\ S75, S76, S77, S78, S79, S80, S81, S82, S84, S85, S86, S87, S88, S89, S90. & \\ \hline S6, S7, S13, S14, S20, S21, S26, S39, S49, S50, S83. & Taxonomy & 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Papers reporting different types of CVs. Change Management and others. We have found that most of the mentions refer to the specification (26.6%), and elicitation activities (25.7%). CVs have also been employed in the Analysis, Validation, Change Management and others, but to a considerably lesser degree. Figure 2 shows the quantity of mentions to every activity in the selected set of papers. It is not surprising that the requirement specification is the activity in which CVs are used most frequently. During this activity, the two types of CVs identified in RQ1 were used. The CVs are used mainly to write the earlier versions of the requirements, informally, during the initial phase of Elicitation, and more formally, during the final step of producing a formal Specification. All papers highlight the need for clear, objective and unambiguous writing. Thus, the papers that report the use of the CVs in the Analysis, Change Management, Validation or Other activities also refer, although indirectly, to the drafting of the requirements specifications. The papers selected for this study focused on elicitation of requirements from the identified stakeholders or software requirements documents, which in turn can include a variety of sources: interviews, questionnaires, workshops with brainstorming, technical documentation review, simulations, modelling and organizational analysis techniques (e.g., Strengths-Weaknesses-Opportunities-Threats analysis). The majority of the selected papers related to requirements analysis focused on requirements conflict identification and resolution tasks. The selected papers reported focused on quality assurance activities of testing and finding faults in requirements. The selected papers related to requirements change management utilized ontologies and taxonomies for handling requirements volatility. Finally, the other activities reported in the selected studies refer to requirements traceability, requirements recovery, requirements engineering methodology (process, methods, and tools) and configuration management among others. To facilitate further analysis to interested researchers or practitioners, Table 9 detailed the selected papers reporting each RE activity. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Primary Papers** & **RE Activity** & **Support Level** \\ \hline S4, S5, S6, S14, S17, S18, S20, S22, S23, S25, S26, S30, S33, S34, S36, & Specification & 29 \\ S40, S41, S45, S48, S49, S58, S63, S64, S65, S75, S76, S78, S85, S90. & \\ \hline S2, S8, S12, S13, S16, S27, S28, S29, S32, S34, S39, S40, S55, S59, S61, & Elicitation & 28 \\ S62, S65, S66, S68, S69, S70, S73, S79, S82, S84, S86, S87, S88. & Analysis & 18 \\ \hline S2, S6, S11, S31, S38, S40, S42, S43, S44, S46, S47, S49, S51, S52, S60, & Analysis & 18 \\ S77, S79, S81. & & \\ \hline S5, S6, S9, S15, S24 (2), S30, S37, S53, S56, S57 (2), S67, S80, S83, S89. & Other & 16 \\ \hline S7, S10, S11, S19, S21, S26, S35, S46, S51, S54, S74, S79. & Validation & 12 \\ \hline S1, S3, S50, S57, S71, S72. & Change Management & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Papers reporting RE activities.