# An Approach to Constructing a Knowledge Graph Based on Korean Open-Government Data
## 4 Results and Discussion: An OGD Graph on the Korean OGD Portal  
This section describes a use case of OGD graph applied to the Korean OGD portal. The vertices of the OGD graph consist of two types of OGDs. One is the data already available to citizens on the Korean OGD portal, and the other is data that can be provided whenever citizens request but not yet available on the portal. We refer to the data already available to users as Opened OGD, and data not yet available as Openable OGD to clarify the two types of data in the following description. In Figure 6, openable OGDs are represented by colored vertices, while opened OGDs are represented by colored vertices with arrows. That is, the OGDs with arrows can be immediately downloadable on the portal. The size of a vertex indicates how relevant the data is to a given user query, and the relevance of the vertex to the query is derived from the applied search engine. When a user clicks a vertex on the graph, he/she can see details of OGD such as the category of the OGD, government agency name, descriptions and keywords. To access the OGD graph with 89,501 vertices on the Korean OGD portal, please visit the portal. Currently, the knowledge graph is only available in Korean [25]. Figure 7 shows a procedure for requesting and delivering raw data. In this example, it is assumed that a user finds raw data of heterogeneous domains to perform decision-making. First, the user searches for OGDs of heterogeneous domains with a single query in the OGD graph, and he/she selects some OGDs for his/her decision-making. Second, the user fills down and submits the raw data request if the selected OGDs are not yet available. Third, a database administrator (shortly, DBA) reviews the raw data request submitted by the user. If the request is appropriate and there is no data limitation, the DBA will extract and upload the raw data to the agency's metadata system. Fourth, after anonymizing personal information such as the social number, mobile number and so on, the raw data is stored in the repositories of the central metadata system. Finally, the raw data is analyzed in a variety of ways to make the correct decision. The data analysis methods such as Text Mining, Statistics and Machine Learning can be selected based on the features of the delivered raw data or the purposes of applications. The focus of this paper is how to collect and organize the OGDs held by government agencies for citizens to easily access the desired OGDs (not how to analyze the delivered raw data). Thus, Figure 8 shows an example of the advantages compared to when the proposed open-data platform and an OGD graph do not exist. We assume that users want OGDs related to \"real estate\" to develop their own applications. Before the proposed open-data platform existed, users could only exploit OGDs that are already opened in the OGD portal and contain the search query (i.e., \"real estate\"). If the users want additional OGDs (e.g., \"real estate with good public traffics\"), they need to search other OGD portals based on their knowledge (or intuition) of the desired OGD location. In addition, official servants may approve or reject the OGD provisions in accordance with their internal policies (or the requester). However, providing users with the proposed open-data platform will allow them to search not only opened but also openable OGDs. In particular, by using the OGD graph, it is possible to find the additional OGDs (such as \"public traffics\", \"schools\", \"Managing fees\", and so on) with the given query at one place. Figure 6: The OGD Graph Applied to the Korean OGD portal. Figure 7: Raw Data Request and Delivery Procedure. Moreover, as the whole openable OGDs are shown in the OGD graph, we can expect a significant increase in the number of raw OGDs requests from users. Since the goal of the Korean government is to promote the use of OGDs significantly and to revitalize the data industries in Korea, the OGD graph was planned and released to enhance citizens' accessibility to OGDs.