# What Is an Open IoT Platform?
## 4 Discussion
### Defining Openness of IoT Platforms?
The open layer of FUSD can benefit device providers to support many complex features in the same consistent manner [60]. Thus, _we observe that open standards are the most important openness type for this kind of IoT stakeholders_. **Operators**: Operators mostly do not have a direct relation with open IoT platforms. Thus, _we observe that openness types of IoT platform are not essential for operators._  
For different stakeholders in the IoT ecosystem, the openness of IoT platform obviously has different meanings. The above insights are based on existing literature and our reflection of how the stakeholders can potentially use the IoT platform for their own benefits. Even though the results show that open-source is the mostly referred openness type among the analyzed papers, in this study we observe that open standards play a more critical role for most of the stakeholders in the IoT ecosystem as seen above. Apart from the platform providers, most of the other stakeholders are concerned with open-source in relation to the openness types of IoT platforms. However, open standards sometimes explicitly or not can be transferred from open-source or open APIs as well. A widely accepted open-source IoT platform can also become the standard in the industry. From the perspective of defining the open IoT platform in the context of different stakeholders' viewpoints, we can adjust these viewpoints among the different identified expressions for open IoT platforms from the analyzed papers, e.g., the change of ThingSpeak from open-source to more open APIs does not make ThingSpeak less open. It is just less open for platform providers and yet even more open and attractive for application providers. Thus, different openness types depend on the stakeholders' needs. The definition from the proposed perspective can also help the IoT platforms owners to make strategical decisions on their designs based on their relevant stakeholders' demands. For example, if an IoT platform plans to attract more application developers to build more IoT applications on its platform, the open APIs may be already enough. However, if the IoT platform plans to provide wider influence across different domains, open-source and open standard may be a better choice. Based on our results, it is also worth noting that there is an increasing interest of research surrounding the use of the term openness in the IoT domain in recent years. In summary, the main findings of our study show that open IoT platforms are characterized by different openness types, while the most dominant type is open-source. The most used platforms among the IoT community are NodeMCU and ThingSpeak. Openness types in general are directly influenced from the interpretation of different stakeholder viewpoints. Below we highlight several open issues:  
* Since none of the analyzed papers define openness, identifying openness dimensions of IoT platforms remains a challenge to be addressed. * It is of utmost importance to find a consensus regarding openness among the different stakeholders to avoid confusion, and preferably agree on a formal definition. * Investigating openness not only from IoT platform perspective, but also considering IoT middleware and frameworks. * To understand how much openness of IoT platforms has penetrated the field and in which domains, a mapping study of the application domains of the identified open IoT platforms would be useful.