Sharing data easily is indispensable for effective and efficient public services. Sharing may be through offering one point of access, and often involves reusing the data in multiple applications across multiple departments and organisations. To make this work, the systems need to be interoperable.

While data exchange is an evident requirement for interoperability, there are fine but crucial distinctions between data format, syntactic, and semantic interoperability. A standardised syntax and data format to store data lets one exchange data, such as creating an SQL database dump in one tool and seamlessly reopening it in another, or lets one send and receive emails that arrive properly in each other’s inbox.

Interoperability at the semantic level concerns the meaning of that data. One may have a format and language to represent data, such as XML, but with a tag <bank> … </bank>, neither the software nor the humans can determine from just that what sort of bank is enclosed within the tags. Such meaning is defined in artefacts including vocabularies, thesauri, and ontologies. A “<fin:bank>” tag in a document is then an implemented version of its definition at the semantic layer, where it has a definition and a number of properties specified, like that the fin:bank is a type of organisation with a board of directors and a location for its headquarters. This enables not only correct sending and receiving of data, but also exchanging data reliably, accessing the right data when querying for information and obtaining relevant data in the query answer, and merging data.

According to the Revised EIF, section 3.5, semantic interoperability "ensures that the precise format and meaning of exchanged data and information is preserved and understood throughout exchanges between parties, in other words ‘what is sent is what is understood’." Besides aforementioned syntactic interoperability, it has the semantic component as well, which "refers to the meaning of data elements and the relationship between them." and "includes developing vocabularies and schemata to describe data exchanges". One recommended way to achieve semantic interoperability between public administrations is to use Core Vocabularies, which is where the terms are specified and disambiguated.

A Core Vocabulary (CV) is a basic, reusable, and extensible specification that captures the relevant characteristics of entities, which can be used to add semantics to data and information that captures the essential characteristics of an entity in a context-neutral manner. Its primary purpose is to provide standardised terms that can be reused across various application domains, typically realised as a lightweight ontology (optionally accompanied by a permissive data shape) and documented in a concise specification. Core vocabularies for SEMIC were created as part of the ISA² program and are described further below in the Core Vocabularies section.

Imagine you are starting a business in another EU country. To complete the registration, you need to submit a criminal record certificate and a diploma certificate to multiple public organisations. In many countries, this process is still manual—people must physically visit different ministries, request documents, and submit them in person or via email. Each organisation may use different formats and terminology, making it difficult for institutions to interpret and process the information correctly, possibly making mistakes during data entry due to terminological confusion that subsequently have to be corrected. Without a common reference vocabulary, these organizations interpret the data differently, making seamless exchange impossible.

Now, imagine an alternative scenario, such as indicated by the Once-Only Technical System (OOTS) for the Single Digital Gateway Regulation, where this entire process is fully automated. Instead of individuals having to visit multiple offices, the ministries and public administrations would communicate directly with each other, exchanging the necessary information in a structured and consistent manner. The citizen could simply grant approval to the administration office to fetch the data from their home country that already had recorded the relevant data. This would eliminate the need for duplicate document submissions and avoid possible data entry issues, thereby reducing the hassle and costs of mobility. This is also the aim of the . Defining the what is one step; the how to achieve it is another.

How can different systems and institutions "talk" to each other effectively at the level of software applications and databases? The challenge is not only technical but also semantic. It is not enough for systems to simply exchange data—they must also be able to interpret the meaning behind the data in a consistent way such that it will not result in errors or so-called 'dirty' (incorrect or incomplete) data. This requires a common language and a (multilingual) structured vocabulary at both the business process level and the IT systems level.

This is where standards to declare the semantics play a crucial role. By using core vocabularies, public administrations can ensure that data and information are structured in a way understood by both humans and machines. Standardised models allow different organisations to recognise and process information without discrepancies, therewith reducing errors and the need for manual intervention. As a result, governments can facilitate seamless data exchange, ensuring that information is accurately shared, interpreted, and processed across systems, leading to more efficient approvals and interactions for businesses, governmental organisations, and citizens.

This handbook is intended for two main audiences: 1) administrative professionals and legal experts, and 2) technical experts and IT professionals.
Public administrations involve both legal/administrative experts and technical professionals. While they may not always “speak the same language”, they must work together to ensure smooth digital transformation. Semantic interoperability provides the common foundation that allows them to bridge their disciplinary differences and find common ground, enabling effective collaboration and thereby contributing to improved public services.
Each intended audience will gain new insights relevant for their respective roles

The SEMIC Core Vocabularies Handbook is designed to practically guide public administrations in achieving semantic interoperability. It provides clear guidance on how to use core vocabularies to create semantic data specifications that align with EU initiatives, how to reuse them, and how to implement them. Additionally, it outlines key use cases demonstrating practical applications of these vocabularies.
The Handbook has two types of content:

The structure of the main part of the handbook is as follows. First, several principal use cases will be introduced, which feature the most common, challenging, and interesting scenarios. It is augmented with other scenarios to indicate further possible usage. This is followed by guidelines for implementation, which includes procedures for how to create new models and how to map existing ones. These guidelines are demonstrated in the tutorials and examples for the use cases. Finally, the appendix contains a glossary of terms for easy reference and usecases not covered in this handbook.