# Wikidata Support in the Creation of Rich Semantic Metadata for Historical Archives
## 2 Overview of the PRiSMHA Environment  
The core of our project is the ontology-driven prototype platform supporting users in the annotation activity. In PRiSMHA, an \"annotation\" is the link from a document (more specifically, a document fragment) and a semantic representation stored in a _Semantic KB_. For example, the document in Figure 1 could be annotated with a link to the semantic representation of the entity representing the FIAT company. In order to add annotations to a selected document, users can click _View or add annotations_ (Figure 2): the system pops up a window (Figure 3) where the user can select an existing entity or add a new one by clicking on _Add (and link) new entity_. In the latter case, after having selected the suited entity type (e.g., _Azienda_--_Company_) and having provided a label (e.g., \"FIAT\"), the user has to fill in a form (see Figure 4) in which all properties characterizing the entity are listed (actually, properties are organized in three tabs, containing _important_, _useful_, and _other_ properties, respectively; see [4]). For all the listed properties but the first one, the user is invited to search the KB to select an existing entity (e.g., _Torino_ for the _ubicata in_--_located in_ property); if no suitable entity is found, the user has the possibility to create a _basic entity_, i.e., an entity characterized only by type and label. This mechanism has been designed in order to enable the user to go on with the description of the entity in focus (e.g., _FIAT_), without being distracted by the description of property fillers; obviously, she will be able to enhance the description of basic entities later on. Figure 2: The page for annotating a document on the PRiSMHA prototype platform. However, as users told us, filling in forms for the characterization of entities to be used in the annotation is a challenging task that is sometimes boring and time consuming. For this reason, in the new version of the prototype we are going to describe in this paper, the user can click _Search on external resource_ (corresponding to the filler of the first \"property\", _Corrisponde eastamente a--Exactly corresponds to_), thus asking the system to search for suggestions provided by external resources, such as Wikidata, in order to pre-fill in some of the properties. In Sections 3 and 4, we will describe in detail how information is retrieved and suggestions are generated. Here, we briefly present the main characteristic of the annotation platform, i.e., the fact that it is ontology-driven. The system's Semantic KB stores the formal descriptions of the entities used in the annotation of documents, as well as the annotation themselves (i.e., the links between entities and documents). It is implemented (by means of Jena TDB 3.6.0 (gena.apache.org/documentation/td) as an RDF triplestore (www.w3.org/RDF, accessed on 10 May 2021)). The conceptual vocabulary used to describe entities is represented by two ontologies, namely HERO and HERO-900. Figure 4: Part of the form for the characterization of an entity (e.g., a company). Figure 3: The modal window enabling users to select or add an entity. HERO (Historical Event Representation Ontology; available at w3 id.org/hero/HERO, accessed on 10 May 2021) is a core ontology organized into five modules:  
HERO-TOP is the upper level of the ontological model, and it is based on the basic distinctions defined in DOLCE [8]: _perdurants_ (including _states_ and _events_), _objects_ (including _physical objects_ and _non-physical objects_, such as _social objects_ as _organizations_ or _social roles_), and _abstract entities_. HERO-TOP also contains relations such as, for example, the _participation_ relation linking _objects_ (e.g., people) to _perdurants_ (e.g., _events_ they participate in). HERO-ROCS is the module devoted to the representation of _social roles_ (e.g., Prime Minister), _organizations_ (e.g., Italian Communist Party, FIAT), and _collective entities_ (e.g., politicians).