# A Reputation Model of OSM Contributor Based on Semantic Similarity of Ontology Concepts
## 3 Methods
### Contributor's Evaluation Reputation
#### 3.3.1 Constructing Geographic Ontology  
Using ontology to express the semantics of volunteered geographic information, concepts are divided into two parts: organizing concept and describing concept. Organizing concept is used to define the concept and the architecture of ontology and to organize the concept into the architecture of geographic information ontology. First, the relationships among the concept are defined by referring to the OpenStreetMap Data in Layered GIS Format [43] and the description of features on OSM Wiki [44], as shown in Table 1. Then, the tree architecture of volunteered geographic information ontology with top-down classification is constructed, which can reflect the different abstractions of volunteered geographic information. The classification tree structure is presently the most commonly used method to construct a hierarchical system. Its characteristic is that each concept can be divided into different levels according to its characteristics, and there is only one parent class and multiple subclasses, which can clearly distinguish the relationship between nodes (parent-child nodes, sibling nodes, etc.). The distance between concepts can be calculated by using the node relationship for the calculation of semantic similarity. [PERSON] discussed the semantic modeling of geographical types from the idea of concept integration [45] and believed that the advantage of ontology with tree structure or concept hierarchy organization was that it could measure semantic similarity on the basis of the distance between concepts [46]. Firstly, this paper defines the broadest concept in the volunteered geographic information field, such as geographic information entities at the top, roads, main roads, highways, and then refines them. Finally, each concept is organized into a classification tree. As shown in Figure 2, the nodes in the classification tree structure represent the volunteered geographic information concept, and the edges represent IS-A semantic relations. The description of the volunteered geographic information entity starts from the top layer, and the description becomes more detailed as it proceeds down. Describing concept refers to describing the definition, semantic relationship, nature, and attributes of volunteered geographic information concept through an ontology conceptual framework. Firstly, this study defines an ontology conceptual framework to describe concept, forms a conceptual framework system, and then determines the nature and attributes of each concept. There are two ways to define the properties and attributes of concept in ontology: one is to inherit the properties and attributes of its parent class through \begin{table}
\begin{tabular}{c c c c c} \hline
**Code** & **Layer** & **Class** & **Description** & **OSM Tag** \\ \hline
5111 & roads & motorway & Motorway/freeway & highway = motorway \\
5112 & roads & trunk & Important roads, typically divided & highway = trunk \\
5122 & roads & residential & Roads in residential areas & highway = residential \\
5131 & roads & motorway\_link & Roads that connect from one road to & highway = motorway\_link \\  & & & & \\
2401 & buildings & hotel & A building designed with separate rooms & tourism = hotel \\  & & & & available for overnight accommodation & landuse = forest, nature = wood \\
7201 & landuse & forest & A forest or woodland & landuse = forest, nature = wood \\
7202 & landuse & park & A park & leisure = park, leisure = common \\
7204 & landuse & industrial & An industrial area & landuse = industrial \\ \hline \end{tabular}
\end{table} 
Table 1: Part of the OpenStreetMap Data in Layered GIS Format. Figure 2: The architecture diagram of volunteered geographic information ontology. inheritance mechanism, and the other is the unique properties and attributes of concept. In the process of defining the properties and attributes of concept, this study pays attention to the standardization of naming and avoids the situation where the same properties and attributes are named differently.