# Architecting Software for the Internet of Thing Based Systems
## 3 Research Method for the Mapping Study
### Frequency and Types of Research Publications  
To answer RQ-1, we discuss the frequency of research publications--as a reflection of the research progression--over the years (ranging from year 2011 to 2018), as illustrated as a bar graph in Figure 6a. In Figure 6a, the horizontal axis represents the number of years, while the vertical axis represents the total number of publication(s) corresponding to each year. For example, in the year 2017, there were a total of 23 published studies, such as [S6, S78, S79] which are relevant to architecting the IoT based software. Please note that the notation **[Sn]** (**n** is a number) represents a reference to studies included in the review, as listed in the Appendix A. The notation also maintains a distinction between the 'Bibliography' and 'Selected Studies' for this mapping study. In general, the graph in Figure 6a reflects a continuous growth of research starting from year 2011 (with 1 relevant study) to year 2017 (having 23 relevant studies). Specifically, the last five years following 2014 can be viewed as more progressive in terms of increased number and diversified types of research publications, such as workshop papers, conference proceedings, and journal articles. The initial published research (from years 2011 to 2013) primarily focused on the unification of cloud computing model to develop the IoT systems [S14, S42, S35]. Later on (during the years 2014 to 2016), the research focused on a diverse set of topics that mainly include, but not limited to, big data systems [S43, S51], security and privacy [S2, S14], web of things [S8, S18], and agent-based systems [S10] that the IoTs drive. Most recently (years 2017 and 2018), the research is focused on fog and edge computing [S64, S40] and self-adaptive software systems [S68, S79] based on the IoTs. Further analysis of the research contributions are discussed later in the subsequent sections of the paper.  
We conclude that the last four years, collectively, can be seen as most progressive in terms of the total number of publications (70/88, i.e., approximately 80% of the total reviewed studies). These years represent the emerging and futuristic research on the role of software architecture to model, develop, evolve, and operate IoT based software systems.  
After discussing the frequency, we must also highlight the types of publications that reflect the diversity of the published research in terms of five distinct categories, namely Workshop Papers, Forum or Summit Papers, Symposium Papers, Conference Proceedings, and Journal Articles. Figure 6b presents the relative distribution of the types of publications. Figure 6b highlights that an overwhelming majority of the research publications (75/88, i.e., approx. 85%) are either conference proceedings or journal articles, which represent not only the proposed solutions, but also their validation to demonstrate the strength and applicability of the research. The research disseminated from conference proceedings and journal articles has mainly focused on the application of software architecture to address the current challenges of big data [S77, S80], system security [S59, S78], and ecosystems [S64, S75] of IoT software.