The term "interoperability" comprising of ‘inter’ (Latin for between), ‘opera’ (Latin for work), and ‘ability’, refers to the intrinsic nature of systems or entities working together to achieve shared goals.

Interoperability in the EU context refers to the capacity of systems or organisations, including public administrations, businesses, and citizens, to collaborate effectively and pursue common objectives across borders. This capability is crucial for providing efficient digital public services, facilitating economic transactions, and supporting the free movement of goods, services, people, and data. The European Interoperability Framework (EIF)[eif], [eif2] and Interoperable Europe Act (IEA) [reg24-903] emphasise that interoperability involves the seamless exchange of information and trusted data sharing across sectors and administrative layers, which is essential for improving policy-making and public service delivery.

Semantic interoperability ensures that the precise meaning of exchanged data is maintained throughout its transmission, adhering to the principle that "what is sent is what is understood", encompassing both the semantic and syntactic aspects of data. The semantic aspect focuses on the meaning of data elements and their relationships, whereas the syntactic aspect deals with the structure or format of the data as it is exchanged. On the other hand, technical interoperability covers the infrastructures and applications that facilitate the linkage between systems and services. This includes aspects such as data representation, transmission methods, API design, access rights management, security, and overall system performance.

Semantic data specifications are detailed, standardised data modelling descriptions that help manage how data is defined, represented, and communicated across different systems. They comprise various artefacts that are both machine-readable and human-understandable, thus supporting consistent interpretation and utilisation across diverse IT environments and stakeholders (e.g. developers, business experts, end users, administrators, etc.).

The SEMIC Style Guide [sem-sg] provides essential guidelines for creating and managing such specifications, covering naming conventions, syntax, and the organisation of artefacts into two critical types of semantic data specifications: Core Vocabularies and Application Profiles.

The Core Vocabularies are semantic data specifications that enable public administrations to standardise data exchange processes, thus enhancing the clarity and consistency of data across different systems and sectors. By leveraging these standards, administrations can effectively bridge the gap between differing data practices, ensuring seamless service delivery that meets the needs of citizens and businesses alike.

Core Vocabularies are simplified, reusable and extensible data models that capture the fundamental characteristics of a data entity in a context-neutral and syntax-neutral fashion [cv-hb]. The SEMIC style guide exlains how the Core Vocabularies [sem-sg-cvs] are context-neutral semantic building blocks that can be extended into context-specific semantic data specifications to ensure semantic consistency. When the Core Vocabularies are extended to create domain specifications and information exchange models, additional meaning (semantics) is added to the specifications, due to the contextualisation.