Research method has a critical role within the empirical studies. In order to converge valid and reliable outcomes, clear cut research methodologies should be applied and reported in the selected primary studies. The types of the research methods can be listed as "Case Study" (in depth investigation with a real-life context), "Experiment" (scientific procedure to test a hypothesis) and "Short Example". It can be derived from Table 5.5 that there is not a tendency towards a research method, considering the fact that the gap between the percentages of the methodologies is not wide. Nevertheless, experimentation is used more often comparing to case studies and short examples to evaluate the system architectures.