## 2 Materials and Methods
### Definition of Search Objectives and Research Questions  
To properly focus the research efforts in the SLR, four search objectives (SO) and a set of research questions were defined, following the approach proposed by [PERSON] and [PERSON] [26], known as the Goal-Question-Metric (GQM) approach. This approach proposes a measurement model composed of three levels of abstraction: (i) Conceptual (Goal), (ii) Operational (Question), and (iii) Quantitative (Metric). At the conceptual level, the objectives were defined to establish, understand, and identify the purpose of the SLR to be conducted. Subsequently, at the operational level, a set of questions was designed based on the objectives obtained at the conceptual level. These questions aimed to focus, characterize, and structure the evaluation of the primary studies identified and related to (un)happiness in agile software communities. The GQM approach suggests establishing a set of metrics related to each question that allow measuring specific aspects associated with a project; however, in this SLR, the metrics suggested by the GQM approach will be developed in future work. The conceptual search objectives (SO) established for the SLR are as follows:  
* Objective 1. Provide basic information, define the scope from a demographic perspective, and allow the identification of relevant sources of information and research in the field of SD in agile software project development from the perspective of happiness or unhappiness in communities. * Objective 2. Help researchers and stakeholders understand the quality, validation, processes, and methods used by the authors of the studies found. * Objective 3. Identify the state of development of the proposals in terms of the results obtained. Figure 1: Process followed for conducting the SLR [25]. Black arrow: normal flow—Blue arrow: stage change—Red arrow: return. * Objective 4. Identify the main research trends, ongoing work, and future work related to SD in agile software project development from the perspective of happiness or unhappiness in communities. Based on the search objectives, five (5) research questions (RQ) were defined along with their respective motivations. The RQs aimed to segment the information found on (un)happiness in agile software communities, thereby supporting the identification of existing research gaps (see Table 1). The results for Objective 1 are presented in Sections 3.1 and 3.2. It is important to highlight that the search for articles was conducted manually, applying the filters established in each scientific database and following the predefined inclusion and exclusion criteria. Additionally, the search string was adapted to each search engine to optimize the retrieved results. During the manual review of the selected articles, new keywords were identified, allowing for the refinement of the search strategy, improved interactions, and an expanded number of relevant contributions on the topic. This methodology was chosen due to the expertise and specialized knowledge in conducting Systematic Literature Reviews (SLR). The advantages of performing a manual SLR include:  
1. Greater objectivity and scientific rigor;
2. Clarity in identifying relevant articles;
3. Comprehensiveness in synthesizing the obtained results;
4. Ease of team discussions regarding the analysis of results and existing gaps;
5. Informed and consensus-based decision-making by the entire team. However, conducting a manual SLR also presents challenges. One of the main limitations is the absence of automated tools, such as generative AI or specialized search engines, which significantly increased the time required to complete the process, totaling nine months. This may lead to an outdated list of primary articles due to the publication of new studies. Additionally, more checkpoints within the team were required to ensure informed and consensus-based decision-making, demanding additional time and availability, which could occasionally result in delays.