# An Approach to Constructing a Knowledge Graph Based on Korean Open-Government Data
## 1 Introduction  
Due to the advances of information and communication technologies (ICTs) such as the Internet and mobile phones, large volumes of data, commonly referred to as \"big data\", are now being produced in public and private sectors around the world. Recently, some services, such as weather forecasting and vehicle navigation, have intended to improve the reliability (or quality) of services by exploiting open-government data (OGD), and several governments are actively disclosing their OGDs. As a result, governments have become one of the largest data producers in various areas, and there is no limit to the sharing and redistribution of OGDs. According to an Organization for Economic Co operation and Development (OECD) report [1], data-driven innovation has become a key part of 21 st-century growth that can significantly improve productivity and social well-being. OGDs are expected to offer a variety of benefits to the community, such as increasing government transparency and accountability, stimulating innovation, and contributing to economic growth [2, 3]. According to [PERSON] et al. [4], since the availability of OGDs in the private sector has increased, numerous OGD portals have been launched to provide a single access point to the government data in various domains. As the number of OGDs and the diverse needs of users have increased sharply, citizens have begun to complain that it is difficult to get proper OGDs in the desired form whenever they need it. This is because only OGDs that governments intend to disclose to citizens are registered with their OGD portals. In other words, ordinary citizens cannot know which government agencies produce and hold openable data (not yet provided to their citizens) and to whom they can request the desired OGDs. Moreover, most citizens want to get a set of relevant OGDs with a single query across heterogeneous domains. For example, suppose a user looking for a set of OGDs submits a query \"car camping\" to the OGD portal to build the web service related to car camping. Currently, most of theOGD portals are based on keyword-based search engines, so they can return only search results (i.e., OGDs) that contain \"car\", \"camping\" or \"car camping\" as index terms. In fact, a set of OGDs containing business hours, the weather of camp sites, the pet admission and the location of pet hospital are more useful for building his/her own web service. The most significant factors that enhance user accessibility to OGDs are for citizens to (1) exactly identify the existing state of OGDs held by government agencies and (2) make it easier to find the relevant OGDs with a single query. To resolve these issues, this paper proposes an open-data platform for auto-collecting the metadata of entire OGDs (including openable data in the future) held by government agencies. In addition, the collected metadata are used to construct a knowledge graph for accessing the entire collected OGDs. To improve the citizens' accessibility to governmental data, we have built the metadata-based open-data platform for real service (www.data.go.kr) with a large-scale OGD of the public sectors. An OGD is linked to semantically relevant ones in the graph, so citizens can easily find the relevant data set as well as the desired data. Our proposal has been applied to the Korean OGD portal (www.data.go.kr), and the OGD-based knowledge graph has also called \"OGD map\". The word \"map\" comes from the fact that citizens can see the locations and open-up status of the entire OGDs. To avoid the confusion with geographical maps, this paper refers to the structure of the knowledge graph as \"OGD graph\" instead of \"OGD map\", hereafter. To the best of our knowledge, this is the first work that constructs a knowledge graph with large-scale OGDs in a real service of the public sector. The remainder of this paper is organized as follows. Section 2 discusses related work. Section 3.1 describes an overview of metadata-based open-data platform.