## 4 Mapping Results  
In this section we introduce the results of the extraction of information from the primary studies. Many publications obtained from the literature were focused on singular aspects of RE in IoT. The publications selected offered significant knowledge regarding the RQs. It is essential to highlight that the 24 primary studies offered answers to more than one RQ. Their answered were sorted according to the RE phases introduced in Section 2. The research questions were answered as follows. RQ-1. Are there any proposals for developing IoT software systems that cover the phases (elicitation, analysis, specification, validation, management) of requirements engineering? In order to answer this question, the classification introduced in Section 2 of this study was considered. According to the primary studies analyzed in this SMS, only one proposal was found that covered the phases of RE; this was the work presented in [30]. The authors presented the _REToT (Requirements Engineering Technology for IoT software systems)_ approach in that article. The aim of REToT was to offer methodological, technical, and tool support for constructing requirements documents for IoT systems. The technology provides constructive processes and models that support the process phases involved in constructing a requirements document. Their proposal comprises an engineering process divided into eight phases: IoT ideation and conception, IoT procurement, IoT analysis, IoT specification, IoT verification, negotiation, IoT evaluation, and management. Although REToT is not a complete IoT software system development methodology, it is dedicated to creating a requirements specification document covering RE activities through UML (unified modeling language) use cases. Other proposals were found in primary studies in relation to this RQ that did not cover all the RE phases. In [31], the authors presented an integrated approach, considering RE techniques for IoT-based smart applications. This was formed over five phases of RE, applying RE techniques for a well-organized requirement management approach. This work supported four of the five phases of the RE process discussed in Section 2. The supported phases were elicitation, analysis specification, and validation. The authors in [32] presented the definition of an RE process for IoT systems. This process is an adapted version of ISO IEC/IEEE 12207:2017 processes. It supports elicitation, analysis, and specification staged of requirements engineering. The authors in [33] presented a methodology that extended the agent-oriented ACOSO-Meth methodology for the engineering of IoT systems. These authors considered the elicitation, analysis, and specification phases. The rest of the proposals obtained from the primary studies, along with the RE phases they covered (less than three), can be observed in Table 4.  
RQ-2. Which RE phases are currently addressed in the field of IoT software systems development? \begin{table}
\begin{tabular}{p{113.8 pt} p{284.5 pt}} \hline \hline
**Type of Study** & **Description** \\ \hline Proposal & An article that presents some new research, e.g., a methodology, method, and technique for RE in the IoT. The degree of novelty is not judged. \\ \hline Formalization & Articles that contain formal or logical language associated with the proposal. Logical operators. Pseudo-code is not considered a formalization. \\ \hline Meta-study & Articles that provide a significant overview of an existing research study. They are considered surveys and reviews. \\ \hline Implementation & Articles presenting tools, plugins, or suites to improve the contribution of the work presented in the primary study. \\ \hline Extension & Articles focused on concepts which had not been considered first in previous proposals. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Type of study classification scheme. The current research trends in RE in relation to IoT software systems development have addressed the elicitation, analysis, and specification phases.