# Research on Driving Scenario Knowledge Graphs
## 3 Methodology: DSKG Construction
### Construction of Ontology for Driving Scenarios
#### 3.2.1 Definition of Classes and Their Hierarchical Structure  
Referring to the widely applicable six-layer scene hierarchical concept, this section also divides the knowledge system of intelligent connected vehicle driving scenarios into six concept classes: Base Road, Roadside Facility, Temporary Change, Dynamic Objects, Environmental Conditions, and Digital Information. Among them, Base Road provides the foundational support for all scenario elements; Roadside Facility is built upon the road structure; Temporary Change describes transient adjustments within Basic Road and Roadside Facility; Dynamic Object acts as an intermediate layer, connecting static and dynamic scenario elements; Environmental Condition characterizes the environmental elements of the scenario and their impacts on the aforementioned concept and vehicle functions; and Digital Information describes all digital data-based information related to vehicles, infrastructure, or both. These concept classes are constructed hierarchically from the bottom layer to the top layer, forming a complete architecture. Each concept class contains specific subclasses, forming a parent-child inheritance relationship among them. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Dataset** & **Year** & **Number of Concept Classes** &
\begin{tabular}{c} **Number of Attributes** \\ **or Relationships** \\ \end{tabular} \\ \hline KITTI [30] & 2013 & 5 & - \\ BDD100K [31] & 2018 & 40 & - \\ NuScenes [32] & 2019 & 23 & 5 \\ A2D2 [33] & 2019 & 52 & - \\ Waymo [34] & 2020 & 4 & - \\ PandaSet [35] & 2020 & 37 & 13 \\ Traffic Genome [36] & 2021 & 34 & 51 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Datasets related to driving scenarios. We utilize the Protege (Version 5.5.0) ontology management software developed by Stanford University for ontology editing and management [38]. During the construction of the domain ontology, we manually input the relevant ontology of driving scenarios. Additionally, we employ the OWLViz module within the software to visually display the hierarchical structure of the domain ontology, as depicted in Figure 4.  
The following briefly explains the core concept classes of the domain ontology of driving scenarios and their subclasses:  
(1) Base Road: This describes the road network and all permanent objects required for road traffic guidance. It can be divided into Road Topology, Road Surface Condition, and Traffic Markings. Figure 4: The hierarchical structure driving scenario. Road Topology can be mapped to the road network and lanes. For complex road topologies such as intersections and roundabouts, they are recorded using a \"road network + lanes\" approach to avoid redundant descriptions caused by the direct classification of road structures. The road network consists of segments and connections, while lanes contain records of actual roads within each segment. Road Surface Condition is divided into Road Surface Material and Road Surface Irregularity. The material of the road surface describes its physical characteristics, including features of materials such as asphalt, concrete, gravel, etc. Road surface irregularity describes whether the road surface has manholes, potholes, cracks, faults, depressions, speed bumps, etc., that affect driving conditions. Traffic Markings are traffic indications drawn on the road surface, which can be divided into directional markings, prohibition markings, and warning markings based on their functions. Directional markings indicate markings on facilities such as roadways, directions of travel, road edges, and sidewalks. Prohibition markings indicate special regulations such as adherence to, prohibition, and restriction of road traffic, which drivers and pedestrians must strictly adhere to. Warning markings prompt drivers and pedestrians to understand special situations on the road, increase vigilance, and prepare for contingency measures. (2) Roadside Facility: This describes all static objects usually placed near the road space rather than on the road.