## 4 Results and Discussion
### RQ2: In Which RE Activities Have the CVs Been Reported?
For example, the use of ontologies and boilerplates enables semi-automatic transformation of natural language requirements into boilerplate requirements (S90). The identification of conflicts and defects is one of the most significant benefits of using CVs during RE. This benefit is closely related to automation and tool support. In this study, the term \"conflict\" refers to requirements that differ and may contradict each other. A good example of these conflicts due to legal cross-references can be found in (S49). Analyzing conflicts in software specifications is crucial when multiple stakeholder concerns need to be addressed (S44). The origin of conflicts can be inconsistencies, redundancies, overrides, and missing parts. A set of rules and the supporting CV (an ontology or taxonomy) can be stored and executed in knowledge-based systems to automatically detect conflicts. This ensures that requirements engineers do not overlook important compliance requirements. When conflicts are identified and resolved, we achieve completeness, correctness and accuracy of requirements and their specifications. CVs have been widely used to improve completeness (S14), thanks to the ease they provide to verify that all the functionality requested by the stakeholders has been included in the requirements, and that all possible inputs (both valid and invalid) have been evaluated and have an adequate response (output). By using CVs and inference rules, an analyst can determine which requirements need to be added/removed to improve completeness (S29). Ontology-driven approaches seem to enable improved quality of requirements in terms of correctness, completeness and consistency (S78). The impact of CVs on quality is addressed especially in 10 selected papers, but it is reported, indirectly, in most of the studies. The researcher used to relate quality to measurable criteria, such as: (a) completeness of individual requirement specifications; (b) existence of traceability relationships between requirements; (c) degree of compliance of individual requirements with the whole set of specifications (S37, S79). Some specific elements such as primary actors, conditions for actions, main flow of events, alternative flows, shall actions, object of action and destination of action, are measured to compute a quality level. Many of these elements are based on completeness, consistency and structure of the requirements. Reusability is one of the most appreciated properties in software development. The CVs help increase reusability from two main perspectives: (a) facilitating the creation of reusable requirements (S05, S52) and (b) offering reusable mechanisms for the search, specification and validation of generic requirements (S22, S30). The application of CVs is frequent in CBSE (component-based software engineering) (S05) and SPE (software product line engineering) (S30), providing greater structure to the planning and elicitation process, but also assisting in the process of configuration/adaptation of requirements from previous developments. All other categories received a lower level of support since we did not find so many specific documents focused on them. However, given the degree of interrelation between the different categories, we cannot say that these categories are of minor importance. Many of the articles that mention aspects of productivity and time reduction are undoubtedly related to cost reduction. The improvements in consistency help the evolution of the requirements and facilitate their maintainability. The validation process is improved by increasing the quality of the communication, control and coordination processes of the development teams, thanks to the reduction in ambiguity. One aspect to highlight is that we have not found a standardized use of the terms to describe the impacts. Some documents associate quality with terms closer to productivity (reduction in development time).