# Towards a Semantics-Based Recommendation System for Cultural Heritage Collections
## 2 Background and Related Work  
### Semantic Technologies in Cultural Heritage  
Cultural heritage refers to the legacy of physical artefacts and intangible attributes of a society inherited from the past, maintained in the present, and preserved for the benefit of the future [1; 3]. Cultural heritage materials are mainly administrated by memory organisations, such as libraries, archives, and museums. Following the recommendations for Open Access to cultural heritage, also known as 'Open Galleries, Libraries, Archives, and Museums' (Open GLAM), many institutions worldwide have digitised their collections, organised the collection data into databases, and published them online. Cultural heritage data is massively heterogeneous in terms of topic, language, culture, data format, target audience, etc., while the items and collections can be \"semantically extremely richly interlinked\" [1; 4]. Semantic technologies have become popular for facilitating data management in the cultural sector as they enhance the interoperability and reuse of cultural data and also enable the development of intelligent services on top of semantically annotated and interlinked data.  
The Semantic Web has been discussed for over twenty years since [PERSON] et al. published the famous paper \"The Semantic Web\" in 2001 [5; 6]. The paper describes an appealing future of the Web providing intelligent services based on machine-readable information. Compared to the current document-based Web, the Semantic Web adds a layer of machine-interpretable data, the metadata, which represents the meaning of resources and documents [1]. This layer of metadata is supported by the RDF (Resource Description Framework) data model and the OWL Web Ontology Language. Both rely on a graph-based data model that explicitly represents relationships between different web resources using triples of the form subject-predicate-object. Each web resource is assigned a unique URI (Universal Resource Identifier). Triples can be interlinked (creating a knowledge graph) to support wider data integration [7]. The aim of this model is to encode the semantic metadata of web resources and link web data to real-world entities in a manner that simulates human comprehension of a domain, facilitating communications between people and data management application systems [8]. An example of an RDF graph is depicted in Figure 1.  
Using the languages and technologies of the Semantic Web, semantic information portals support the management and provide access to semantically annotated data [10; 11; 12]. They facilitate the content publishers' work by collecting data from various web sources exploiting the homogeneous, ontology-based representations and interconnections of semantic metadata [13]. From the view of end-users, they provide intelligent services for accessing and visualising aggregated data, exploiting their underlying structure. During the last two decades, several semantic information portals have been established on top of cultural heritage collections, such as Europeana, the largest European digital library [14; 15], and the Sampo portals focusing on various aspects of Finland's cultural heritage [16].