## 4 Implementation of an Open Data Platform in Accordance with the Proposed Approach
### Introducing Hazelnut Trait Ontology
It can detect the following gases: carbon monoxide from 1 ppm to 1000 ppm, nitrogen dioxide from 0.05 ppm to 10 ppm, ethanol from 10 ppm to 500 ppm, hydrogen from 1 ppm to 1000 ppm, ammonia from 1 ppm to 500 ppm and methane greater than 1000 ppm. Router 2 has three sensors such as soil moisture, rain and BH-1750 light level. The soil moisture sensor categorizes its measurements as dry soil, humid soil and in water. The rain sensor, actually a raindrop sensor, does not measure rainfall. It categorizes its measurements as raining, rain warning and not raining. BH-1750 sensor can measure light intensity from 1 lx to 65535 lx. Router 3 has only one sensor named MPU6050, which is 6 axis acceleration and gyro sensor. These sensors were defined for representation using abbreviations by a set of named constants which are illustrated on Table 4.  
Coordinators and their routers are illustrated on maps on open-data platforms according to their latitude and longitude information. Platform users can access the detailed information of WSNs by following the link on coordinator tooltips. Each one of the sensors, routers and coordinators can be visualized as hierarchical nodes on the platform; and platform users can access sensors' data, which are measured in the last five minutes and visualized in appropriate graphs by using clickable features of the routers' icons. Figure 3 shows how each component of WSN is viewed on the open-data platform. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sensor** & **Measurement** & **Abbreviation** \\ \hline BH1750—light level sensor & Light intensity & LI \\ \hline BME 280 temperature humidity barometric pressure sensor & Weather temperature pressure altitude & WT \\ \hline MPU6050 6-axis acceleration and gyro sensor & Gyro measurement range & GR \\ \hline Rain sensor & Rain rate & RR \\ \hline Soil moisture sensor & Soil moisture & SM \\ \hline UV sensor module Arduino ultraviolet ray I2C & Ultraviolet & UV \\ \hline MICS-4514 carbon monoxide nitrogen oxygen sensor & Carbon monoxide Nitrogen dioxide & CO \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Enumerating measurements types of sensors. It is a well-known fact that reading sensor inputs and transforming them into a meaningful format requires using microcontrollers. Therefore, Arduino, which is an open-source member of family of electronic microprocessor boards, based on easy-to-use hardware and software, was used as router and coordinator devices within the WSN. Other reasons to use Arduino as router and coordinator devices are as follows: it is inexpensive; its IDE runs on cross-platforms and easy-to-use; and its hardware and software are open source [60]. Furthermore, it ensures key features to collect both economic and practical benefits for researchers [61]. Raspberry PI, which is a low-cost and single-board computer, is used for interfacing the coordinator device through serial ports to receive data assembled from routers. Raspbian which is a kind of operating system based on Debian developed for Raspberry Pi can be freely accessed and is downloadable by any users. In addition, Raspbian is a commonly preferred operating system option for Raspberry Pi computers and freely available community project under active development. Therefore, it was considered the suitable operating system option that will run on the Raspberry Pi computer, which plays the manager role of established WSN. Furthermore, a Python program was developed to read raw sensor data gathered from a coordinator device through a serial port. This program is also responsible to store raw data in a relational database using RESTful web service operations. XBee module, which supports multiple protocols, is highly configurable and consists of small radio frequency (RF) devices that transmit and receive data over air using radio signals [62]. It was used to transmit data wirelessly between routers and the coordinator. Each XBee device is configured as Application Programming Interface (API) mode within the built WSN.