# What Is an Open IoT Platform?
## 3 Results
### Q2: Which Are the Openness Types of IoT Platforms? To answer this question, we used fields F7-F11 from Table 1. From the classified data we were interested to find out what makes the open IoT platform. However, from the F9 field, only three studies provided some directions of openness definitions related to IoT platforms [33; 34; 35]. The first study proposes an open IoT service framework [33]. Within this proposal, the authors define their open IoT platform by the following categorization: _Device Platform:_ for connecting and cooperating things with open IoT platforms; _Planet Platform:_ for server related aspects; _Mashup Platform:_ for new integrated services and devices to be available over the Internet; and _Store Platform:_ an online store including applications or links for user services. **Observation:** Even if the authors claim that they define an open IoT platform [33], there is no clear definition of openness as such. A very close study related to openness dimensions of platforms, specifically addressing industrial Internet platforms, was analyzed by [PERSON] et al., 2019 [34]. This study provides insights regarding the differences in the degree of platform openness, for instance how open the platform is in terms of the involvement of third-party developers. This involvement varies based on several aspects: (1) the access to information; (2) the rules that allow the usage of a platform; and (3) fee (license fee). The openness dimensions are defined in terms of: _Demand-side user (end user), Supply-side user (application developer)_ and _Platform-provider-and sponsor-related openness_. The more open the platform is related to these three dimensions, the more easily different parties can use that platform. **Observation:** Even if the authors [34] provide different insights related to openness dimensions of platforms, they do not explicitly define what is an \"open\" IoT platform. However, an interesting insight out of this study [34] is that stakeholders can play an important role for this matter, thus we bring the stakeholders view later in discussion part of our paper. The third study by [PERSON] et al. [35] presents some directions towards understanding IoT platform definitions in general by discussing the main characteristics. In this study, [35], specifically they present high-level features of the open-source projects, such as connectivity/device management, data storage and management, data analysis, data visualization, development tools and platforms,  
Figure 4: Seven most cited open IoT platforms. edge/fog computing, integration and interoperation as main characteristics for open-source projects related to IoT platforms. **Observation:** Even if the authors [35] provide and place several open-source projects into different characteristics, they do not provide the openness definition and neither the openness types of IoT platforms. Further on, we analyzed extracted data from F7, F8 (134 used and 56 respectively indicated) and F11. Table 2 shows 25 open IoT platforms that are mapped with the identified openness types. Among them the most common denominator is open-source. For example, 45 studies mark NodeMCU as open-source, and respectively 29 for ThingSpeak. We can consider each openness expression of the different open IoT platforms as a vote for what makes them open, because the specific IoT platform is referred to with different openness types based on author opinions. With Figure 5 we observe that most of researchers consider open IoT platforms from an open-source perspective. Interestingly, for ThingSpeak there are 12 papers in which the authors do not specify the openness type, but just mentioning ThingSpeak as an open IoT platform. Other identified openness types based on \"used and indicated\" categories of papers are open standards, open APIs, and open data, and some of the papers analyzed do not even specify the openness type of the platforms they use.