## 3 Analysis of the System
### New Ontology  
An ontology is a specification of a conceptualization [35; 36], which defines and classifies concepts, entities, and the relationships between them. An ontology integrates entities, such as classes or dependencies, and formal axioms to limit the interpretation and well-formed use of them. Classes provide a mechanism of abstraction to group resources with similar characteristics. Two class identifiers have been predefined in the OWL semantic Web language: the _Thing_ and _No Thing_ classes. The _Thing_ extension is the set of all individuals, while _No Thing_ it is the empty set. Each OWL class is a subclass of _Thing_[37]. The individuals represented in the extension of the class are the instances of the class. When a class is defined as a subclass, their individuals are a subset of the individuals contained in the parent class. Two main categories of properties are defined in OWL: object properties, which link individuals; and data type properties, which assign individuals to data values. On the other hand, range and domain are axioms used during the inference process, which is the process of deduction that allows knowledge to be obtained from known data and existing relations in the ontology. A range axiom assigns a property to a data range, specifying the range of the data values. A domain axiom assigns a property to a class description, specifying the extension of the indicated class. A problem that was found during our research is that obtaining data from multiple cultural institutions via Europeana is not unified, since every institution has used their concrete terms to catalogue their collections. When a new application is created, a different query has to be implemented to access each institution, i.e., University College of London (UCL) or Israel Museum. Moreover, the keys that were used in each query were different. Each institution has the information to search in a different concept, i.e., the name of the shabti. A new ontology was designed to integrate different institutions and thus be able to obtain data with just one query. This ontology was also designed to specify the keys that had to be used in the query. There are three general subclasses of _Thing_: _Museum_, _proxyRelation_ and _mediaRelation_ (see Figure 10). The extension of the class _Museum_ refers to cultural institutions, such as the UCL,Fitzwilliam Museum or Israel Museum. Europeana includes _Cultural Heritage Objects_ (CHO) that are associated to concrete proxies. The class _proxyRelation_ specifies which URIs are significant for a museum. Simultaneously, the class _mediaRelation_ specifies the possible media relations of a museum, i.e., photos of the object. The class _Museum_ has different data properties. _key1_ and _key2_ specify the URIs used to search in that museum. For example, _key1_ = [[http://purl.org/dc/elements/1.1/type](http://purl.org/dc/elements/1.1/type)]([http://purl.org/dc/elements/1.1/type](http://purl.org/dc/elements/1.1/type)) specifies that the concept _type_ of [[http://purl.org/dc/elements/1.1](http://purl.org/dc/elements/1.1)]([http://purl.org/dc/elements/1.1](http://purl.org/dc/elements/1.1)) will be used to search for the term \"shabti\". The property _dataProvider_ specifies the name of the institution, i.e., \"UCL Museum\". A museum is linked to a general provider and the property _provider_ is used for that purpose, i.e., \"AthenaPlus\". This property could be omitted, but the query would not work due to a time out. Data has to be filtered to work in a reasonable time. All the used data properties are of type _xsd:string_. The classes _proxyRelation_ and _mediaRelation_ have two data properties: _relation_ and _value_. _relation_ specifies the URI used to link the concept indicated by _value_ with the proxy of the CHO (_proxyRelation_) or just the CHO (_mediaRelation_).