## 3 Overview of DSML4 PT Language  
As previously introduced, DSML4 PT is a modeling language whose syntax is based on a metamodel that enables modeling IoT-based public transportation applications according to different viewpoints and facilitates the MDE of such applications for different public transportation platforms. This section briefly discusses the main components and features of this language. Complete specifications of DSML4 PT's syntax and semantics definitions, as well as its modeling and code generation features, can all be found in [5]. The metamodel, which constitutes the abstract syntax of DSML4 PT, provides the connections and main elements of public transportation systems, including IoT technologies. Related metamodel entities and their relations are derived based on an examination of various public transportation specifications (such as [4,85,86]) and the requirements of developing IoT software for public transportation systems discussed in [3]. The metamodel is divided into three different viewpoints, named IoT Core, Public Transport, and Service/Cloud. DSML4 PT's IoT Core viewpoint includes elements (such as Controller, Port, Actuator, Sensor) that define a generic IoT device, regardless of the characteristics of public transportation devices. The Public Transport viewpoint includes elements that describe the unique features of a public transportation system. In this viewpoint, the difference between public transportation devices from general IoT devices is defined at the metamodel level. It contains elements and relationships that enable the modeling of the domain. As indicated in [5], DSML4 PT's Public Transport viewpoint supports special hardware, standards, and protocols created for general use starting from the processor level. Microprocessor families working with the operating system are reflected in the metamodel in great detail from this \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Study** & **IoT-Based Public Transportation Modeling Features** & **Supporting Platform/OS/Language** & **IDE/Tool Provided** & **Use Case Included** & **Usability Evaluation** \\ \hline [PERSON] et al. [16] & Traffic and Road Safety & Cloud, REST Services & Yes & Yes & No \\ \hline [PERSON] et al. [71] & Traffic Lights, Lighting Systems & Cloud, Scada Systems & Yes & Yes & No \\ \hline  & & Secure Access Modules, & & & \\ [PERSON] et al. [72] & Fare Collection & \begin{tabular}{c} Near-Field Communication, \\ Linkerforge \\ \end{tabular} & Yes & Yes & No \\ \hline ENACT [15,40] & Train Control & EDI Test Bed & Yes & Yes & No \\ \hline [PERSON] et al. [63] & Cloud and Privacy & Cloud & Yes & No & No \\ \hline [PERSON] and [PERSON] [14] & Wireless Sensor Networks & Android, MySQL, Java & Yes & Yes & Yes \\ \hline [PERSON] [73] & Sensor Tracking & Web & Yes & Yes & Yes \\ \hline [PERSON] et al. [31] & Security & \
\begin{tabular}{c} Raspberry Pi, \\ PandaBoard, Java, \\ C/C++ \\ \end{tabular} & Yes & Yes & No \\ \hline BRAIN-IoT [37] & Security and Privacy & Cloud & Yes & Yes & No \\ \hline [PERSON] et al. [81] & Mission-Critical Systems & CHESS & Yes & No & No \\ \hline [PERSON] et al. [84] & Quality of Experience & - & No & No & No \\ \hline  & & Wide range of platforms, & & & \\ Our Study & All above &
\begin{tabular}{c} languages and OS \\ including above via \\ model trans. \\ \end{tabular} & Yes & Yes & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 2: MDE studies of IoT-based intelligent transportation and public transportation. point of view. Finally, the Service/Cloud viewpoint of the language defines the elements such as ServiceApp, MonitorApp, SmartPhone for service and cloud-based mass transit. They are specialized for using the services of simple microcontrollers. In this perspective, there are smart phone and computer application elements that provide the monitoring of public transportation IoT devices.