# Representing and Validating Cultural Heritage Knowledge Graphs in CIDOC-CRM Ontology
## 1 Introduction  
The COURAGE (Cultural Opposition: Understanding the Cultural Heritage of Dissent in the Former Socialist Countries) project aims to highlight the variety of alternative cultural scenes that flourished in Eastern Europe under strict government regulations prior to 1989. It was established to investigate the methods of cultural opposition during the socialist era from 1950 to 1990 [1]. The COURAGE project has an online resource description framework (RDF) store represented by high-quality linked data on cultural heritage (see Figure 1). The collection entity, the main focus of the project, is one of the primary entities in the COURAGE registry. Each collection has one or more linked featured items. All the following entities are connected to one or more collection(s) via one or more role(s). Some of these entities are historic people, groups, and organizations that played significant roles in the collection's history. Furthermore, the store included events that were significant in the history of collections [2]. Figure 1: COURAGE registry. Entity types and properties of COURAGE are organized into an ontology structure [2]. The base type in the schema is the historical item, which is used for describing entities from a historical viewpoint (see Figure 2). The main properties of this type are name, location, short description, and website. Subclasses of historical items focusing on content include collections, featured items, and publications. The second type at this level is the interview, which is considered a source of information. The third type is an event that has a start and end date and is linked to collections and agents. Agents are the most complex types in the schema; they can be people, groups, organizations, or networks. Agents may have various, time-limited roles in the lives of collections including creator, funder, operator, etc. CIDOC-CRM (CIDOC Conceptual Reference Model) is a formal ISO standard ontology that aims to integrate heterogeneous sources of cultural heritage information. This model can be used by cultural heritage institutions to describe their entities and improve knowledge sharing [3]. CIDOC-CRM provides definitions and a formal structure for the concepts and their relationships in cultural heritage documentation. CIDOC-CRM starts at the top level, with the classes of persistent and temporal entities. As a result, it can be regarded as a universal ontological model capable of describing people, objects, events, and activities alike [4]. It was developed for museums by the International Committee for Documentation (CIDOC) of the International Council of Museums (ICOM) to formalize the historical data in the cultural heritage field. CIDOC-CRM acts as a mediation between diverse cultural heritage concepts by providing the needed semantic glue to translate the heterogeneous datasets into cohesive sources (in Figure 3). Figure 2: The main types of the COURAGE ontology. The CIDOC-CRM was selected for this research as it is the dominant schema in the cultural heritage field [6; 7; 8]. Using CIDOC-CRM also improves semantic integration and interoperability, as it is a standard and many datasets and research tools are using that representation. It already has many necessary concepts for archival descriptions, such as people, collections, events, and others [9]. This paper aims to prove the possibility of semantically mapping and aligning the COURAGE dataset, which represents an important part of recent European history that is hard to find in other datasets, to the CIDOC-CRM ontology [10]. By this mapping, the interoperability of this valuable data will be improved, and the COURAGE dataset may be linked and integrated with other populated CIDOC-CRM ontologies. Therefore, this paper introduces a mapping methodology and a validation technique to check the generated model. We semantically transferred the COURAGE dataset to the CIDOC-CRM ontology according to predefined mapping rules. These rules were created based on a consolidated set of principles and a console-based application.