# A Semantic Model for Enhancing Data-Driven Open Banking Services
## 2 Background Concepts and Related Work
### Preliminary Concepts  
This subsection is devoted to describing a set of relevant concepts to make the paper more self-contained.  
* Ontology [15]. This is a description framework that provides a formal representation of the real world, shared by many users, by defining concepts and relationships between them. It defines a set of axioms and primitives to represent a specific domain of knowledge or discourse. In computer science, ontology refers to an artifact designed to allow the formal modeling of knowledge about a domain. Ontologies are part of the standards developed by the W3C consortium for the semantic web. In the semantic web, they are used to standardize vocabularies that facilitate the exchange of information between systems. This standard provides services to solve queries and to populate and publish knowledge graphs [16] so that they can be reusable and facilitate interoperability between heterogeneous systems and databases. Instances of ontology classes and properties annotate data or resources semantically. Furthermore, the reasoning capabilities of ontologies allow semantic web applications to infer implicit knowledge from explicitly expressed knowledge, enabling the creation of intelligent applications.
* RDF [14]. To define an ontology in the context of web semantics, we used the standard language RDF, according to which resources are described in terms of properties and values. RDF statements are represented as triples, consisting of a _subject_, a _predicate_, and an _object_. RDFS (RDF Schema) [17] semantically extends RDF to define resource classes and the properties that those classes describe. RDFS provides the mechanisms for explaining the specific RDF vocabularies for each application. Although the expressiveness of RDFS is still insufficient for all applications, it is enough for data exchange and allows semantic languages to be built on top of it. However, for many other applications, it is necessary to have other characteristics, such as cardinality constraints, transitive properties, inverse properties, and range. When used for a specific class, it is able to express classes as unions or intersections of other classes. In addition, ontology languages should meet other requirements, such as having a well-defined syntax, being based on formal semantics necessary for reasoning, and supporting efficient reasoning mechanisms while maintaining expressiveness.
* OWL [17]. Proposed by the W3C Ontology Working Group, this is a semantic markup language for publishing and sharing ontologies on the web. OWL is equivalent to a very expressive description logic, where an ontology corresponds to the Tbox [18]. This equivalence allows language to exploit the results of researchers in the logic of descriptions. OWL extends RDF and RDF Schema, with the main goal of bringing the expressiveness and reasoning power of description logic to the semantic web. OWL provides two sublanguages: OWL Lite for simple applications and OWL-DL, which represents the subset of the language equivalent to the logic of descriptions, the reasoning mechanisms of which are complex. A new version of this language is OWL 2 [13], which includes new functionalities, e.g., keys, property strings, data ranges, and qualified cardinality constraints. These new features are oriented towards increasing expressiveness.