# SOLIOT--Decentralized Data Control and Interactions for IoT
## 9 Conclusions and Outlook  
This paper presents SOLIOT, an approach to merge concepts following Linked Data Platform and SOLID patterns aligned with IoT requirements. The respective capabilities and requirements have been discussed according to functional, non-functional, protocol- and data-related aspects. The basic functionality is shown through a prototypical server implementation, together with the provisioning of Web and IoT protocol endpoints, discovery mechanisms and how self-descriptive representations can model a Digital Twin. SOLIOT outlines how the latest developments form the web community can be transferred to IoT challenges. The solely resource-driven view on the representation simplifies both the consumption and interaction with the thereby supported Digital Twins, and allows visiting clients to directly understand the Digital Twin itself but also helps developers and system integrators to adjust their workflows and APIs. This is achieved by the reduction of interaction patterns together with the self-descriptive nature of all involved concepts, promising a decrease of the overall integration complexity and increasing maintainability. The Digital Twin outlines both its content, interaction patterns and authentication model to the client. In addition, this is not only the case for the consuming applications, usually with higher computational power, but also for the restricted devices acting as the information sources. The proposed approach still holds significant gaps. While the most crucial interaction patterns have been mapped, the true potential of the SOLID to IoT approach demands the complete coverage of all specified discovery mechanisms. The IoT mappings do not yet cover all headers and response mechanisms of a full-sized SOLID solution. In addition, the identity and authentication potentials of WebIDs are not sufficiently reflected at this stage. This is especially relevant, as a decentral yet reliable and at the same time simple to implement identity mechanism is essential for any scalable IoT approach. The core challenge is certainly the proper treatment of a physical Thing and its Digital Twin moving across networks, organizations and life cycles. The thereby created challenges towards interoperability, legislative obligations, ownership rights etc. are still not sufficiently understood. Nevertheless, the general feasibility of SOLIOT is demonstrated through a CoAP and MQTT binding, more powerful protocol stacks have not been tested yet. In particular, the OPC UA specifications define not only a communication protocol but also an elaborated interaction and information model. Respective endpoint adapters, data lifting and lowering modules, and appropriate mappings for authorization need to be developed to examine the characteristics further. The provided analysis showed a series of relevant but still unaddressed requirements. As directly visible though the significant number of gaps shown in the mapping tables, more work is necessary  
Figure 9: Variance of measures presented in Tables 8 and 9 (in milliseconds, 10 clients requesting each instance). for a complete picture. Even though one can certainly question whether each IoT concept needs to address all outlined requirements, the awareness of their relevance and how they impact the desired solution is necessary. This work should be regarded also as an inspiration for further approaches by stating the current possibilities but also limitations. At the core of SOLIOT is the translation of established and clean interaction patterns from the Web into the IoT where all necessary information is explicitly described and available for look ups. The further decoupling of IoT communication will introduce a new flexibility and dynamics into device-to-device networks. An ongoing integration of previously separated and segregated OT networks with the global Internet network can be stated. This requires a shared understanding on how 'Things' need to interact and how they need to be described.