# A Survey of Techniques for Discovering, Using, and Paying for Third-Party IoT Sensors
## 2 Survey Methodology
### A Taxonomy of Challenges for Devising the Global Sharing of IoT Devices  
In this section, we propose a taxonomy of challenges that we use to review and classify work related to sharing IoT devices in order to devise the global sharing of IoT devices. Table 2 presents the proposed taxonomy. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Taxonomy Categories** & \multicolumn{4}{c}{**Challenges of Global Sharing of IoT Devices**} \\ \cline{2-5}  & **Scalable** & **IoT-Owned** & **Interoperable** & **Comprehensive** \\ \hline \hline \multirow{7}{*}{\begin{tabular}{c} Describing IoT \\ devices and their \\ data \\ \end{tabular} } & \multirow{7}{*}{N/A} & \multirow{7}{*}{N/A} & \multirow{7}{*}{N/A} & Description of & Description of all or most \\  & & & & heterogenous IoT & aspects of IoT devices, \\  & & & & devices, their data, & including the \\  & & & & and supporting & cost/payment of using \\  & & & & heterogenous IoT & IoT devices and \\  & & & & applications & integration details \\ \hline \multirow{7}{*}{\begin{tabular}{c} Discovering IoT \\ devices \\ \end{tabular} } & Registration of the & \multirow{7}{*}{\begin{tabular}{c} Registration of the \\ large and \\ ever-increasing \\ number of IoT \\ devices \\ \end{tabular} } & Registration of & & & \\  & & & & without owning the \\  & & & descriptions of the \\  & & & devices & IoT device \\ \hline \multirow{7}{*}{\begin{tabular}{c} Querying IoT devices \\ \end{tabular} } & Query of the large & Query IoT devices & & Query heterogenous & comprehensively \\  & and ever-increasing & & & IoT devices and their & including cost/payment \\  & & & & data & and integration \\  & & & & capabilities \\ \hline \multirow{7}{*}{\begin{tabular}{c} Indexing IoT devices \\ \end{tabular} } & Index of the large & Index of devices & Index toT devices & & \\  & & & without any control & IoT devices & N/A \\  & & & & from any entity & \\ \hline \multirow{7}{*}{\begin{tabular}{c} Using IoT \\ devices \\ \end{tabular} } & Integrating IoT & \multirow{3}{*}{\begin{tabular}{c} Integration of the \\ large and \\ ever-increasing \\ number of IoT \\ devices \\ \end{tabular} } & Integration of the & \multirow{3}{*}{\begin{tabular}{c} Integrate IoT devices \\ globally without any \\ control from any \\ entity \\ \end{tabular} } & Integrate IoT & & & \\  & & & globally without any & heterogenous IoT & N/A \\  & & & control from any & devices and obtain & \\  & & & entity & their data & \\ \hline \multirow{7}{*}{\begin{tabular}{c} Paying IoT devices \\ \end{tabular} } & Payment of the large & Payment of IoT & \multirow{3}{*}{\begin{tabular}{c} Dealing with \\ heterogenous \\ payment of IoT \\ devices \\ \end{tabular} } & \multirow{3}{*}{\
\begin{tabular}{c} Payment of IoT \\ devices globally \\ without any control \\ from any entity \\ \end{tabular} } & \multirow{3}{*}{
\begin{tabular}{c} Dealing with \\ heterogenous \\ payment options to \\ pay for using IoT \\ devices \\ \end{tabular} } & \multirow{3}{*}{N/A} \\  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Taxonomy of challenges of devising the global sharing of Internet of Things devices. This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, as well as the experimental conclusions that can be drawn. 1. [label=0.,leftmargin=*]
2. Describing IoT devices and their data: This category includes existing techniques (e.g., ontologies, data models, and schemas) that have been proposed to describe IoT devices and their data. IoT device and data descriptions are standards set of information about the software, hardware, system, and measurement capabilities, which can be used to describe sensors on IoT devices and their data (e.g., type, name, data unit, and location). Describing IoT devices is the key to discovering them and sharing them because it provides the necessary information that allows IoT applications to find the required IoT devices and IoT data.