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DE4A, the project that has explored and piloted across borders to create an effective and efficient implementation of the once-only principle (OOP) for Member States, has come to an end after three years and four months.

On 24th May 2023, in the final review with the European Commission, the multidisciplinary results of the project were presented, addressing architectural, technical, semantic, legal and organisational barriers to cross-border interoperability in the context of the modernisation of EU public administrations (Once-Only Principle, Single Digital Gateway, Once-Only Technical System). Such results are expected to have a significant impact, making it much easier for Member States to meet the obligations resulting from the entry into force of the Single Digital Gateway Regulation. This Regulation requires that a list of 21 types of administrative procedures, currently available online to national users, be offered to cross-border users, with automated data exchange between public agencies, required to fulfil these procedures, e.g. applying for study grants, asking for recognition of academic titles or requesting proof of residence.


The main results have been the following:


  • Hands-on experience and knowledge for DE4A Member States: The project has provided the 8 participating Member States and other stakeholders with the necessary experience to address the short, medium and longer term challenges in the contexts of Once-Only, Single Digital Gateway and effective and integrated cross-border delivery of public services to citizens and businesses in the context of the modernisation of these public services across the EU.

  • DE4A Multipattern architecture for the cross-border exchange of evidence between the Member States.

  • DE4A Connector, the component that establishes the cross-border communication between the Member States for the exchange of evidences over an eDelivery network.

  • DE4A Self-Sovereign Identity Framework.

  • DE4A semantic components required for a common understanding to facilitate the cross-border exchange of information between public authorities.

  • Legal insights on the challenges for the implementation of the SDG.


The main results are released as open source and can be found, together with documentation and licensing information, on the DE4A Wiki and DE4A Github. Full information on project deliverables and academic publications can be found on the DE4A public deliverables and academic publications pages.

EU eGovernment landscape: DE4A Summary report

The DE4A project has conducted extensive activities to provide overview and analysis of the EU eGovernment landscape. This report summarizes the key findings from the inventory activity, which focused on various aspects of eGovernment implementation, adoption and barriers. The activities revolved around identifying and analyzing the deployment of cross-border integrated Digital Public Services, as well as the status of existing solutions supporting Electronic Identification, Authentication and Trust services (including European Digital Wallets (eIDAS / eIDAS v2), the Single Digital Gateway Regulation (SDGR) and the Once Only Principle (OOP) implementation.
For a summary of the main findings, please consult the document "EU eGovernment landscape: DE4A Summary report"

DE4A Final Event


DE4A is honoured to invite you to the DE4A Final Event (online, April 12th 2023) which will provide a quick, easy-to-understand overview of the project's results and lessons learnt. Find out more about the agenda and register here

DE4A at the Austrian IRIS symposium

IRIS symposium is an Austrian conference for legal informatics, in which eGovernment is also included in the conference programme. The conference takes place yearly in Salzburg/Austria. In the 2023 Austrian consortium consisting of BRZ/BMF, which is also involved in DE4A, explained Austrian findings and experience regarding Once Only Principle in the Single Digital Gateway Regulation (project, processes, architecture, environment and influence factors).

DE4A was part of the presentation at IRIS symposium, as an influence factor for the SDG Once Only realisation in Austria. The presentation took place on 23. February 2023 in the session "eGovernment I"; around 20 persons were in the audience (offline and online).

DE4A Moving Abroad pilot, mission accomplished


The DE4A Moving Abroad pilot has been working for some time. Now we have two countries live with pilot services (Spain and Slovenia) for the use case enabling to request an extract or copy of civil status (Birth and Marriage) certificates. Slovenia (data provider) is providing both types of certificates to the Spanish online citizen portal (data consumer). Additional cross-border combinations also involving Luxembourg, Romania and Portugal will soon be launched also for registering a change of domicile address (with subsequent deregistration of an old domicile address in the case of Portugal).


Getting hold of your fundamental evidence for life in the EU is not always easy nor has it been easy for clerks to verify the authenticity of such evidence, Marriage & Birth Certificates and Domicile addresses. Moving to a new country should be easy and you should not have to worry about basic administration: the EU Member states will support you.


Today it often takes several weeks and requires obtaining documented proof that must be uploaded or sent by email. The piloted solution enables company citizens to securely send evidence across borders without language barriers. We can now send Member States structured evidence within minutes. It saves time, effort, and money to complete the fully online procedures and provides public authorities with reliable, structured, and authentic data they can easily process.


Public Authorities and pilot testers that are involved are enthusiastic about the new solution and the possibilities it will offer on a large scale.


Main components reused were the DE4A Once Only Technical System for securely exchanging authentic information, and eIDAS to securely authenticate citizens. The infrastructure has been integrated with population registries and public authorities provide modern services for citizens. These basic certificates are used in many services and we expect that new public agencies and Member states can and will reuse the services in other procedures.  


See the pilot videos and read the lessons learnt at the Moving Abroad microsite.

DE4A pilot Doing Business Abroad, successfully completed

In January 2023 Sweden, Romania, Austria and The Netherlands successfully completed the Doing Business Abroad pilot as part of the DE4A Large Scale Pilot.


The Member States developed international infrastructures to support cross border activities for companies. Main components were the DE4A Once Only Technical System for securely exchanging authentic information, and eIDAS and SEMPER for reliable authentication and authorization. The infrastructure has been integrated with business registers and public authorities providing services for companies. It also enables public authorities to stay informed about any events that occur in the company, so they can make sure to provide the correct services.


In a situation without the infrastructure, registering a new business activity can take up to several weeks and requires obtaining documented proof that must be uploaded or sent per email.

The piloted solution enables company representatives to notify new business activities in other Member States, within minutes. It saves time, effort and money to complete the fully online procedures and provides public authorities with reliable, structured and authentic data that they can easily process.

Public Authorities and company representatives that were involved are enthusiastic about the new solution and the possibilities it will offer on a large scale.

For more information, see the Doing Business Abroad microsite

Launch of services in the final phase of the Studying Abroad pilot

The Studying Abroad pilot of the DE4A project aims at demonstrating in practice the benefits for students and competent authorities of realizing across borders the principles of Once-Only and digital-by-default. The pilot is proud to announce that several cross-border educational services have been launched for the final pilot phase.

The services largely correspond to the fully online procedure of the 'Studying' Life Event in the Single Digital Gateway Regulation (SDGR), which allow students from Portugal, Slovenia and Spain to easily pre-enrol for a 1st or 2nd Bologna degree study abroad at the University Jaume I in Spain, the University of Lisbon, or any university in Slovenia. Spanish and Portuguese students can also apply for study grants at the Jozef Stefan Institute in Slovenia. Students use their national eIDs to access the services and can explicitly request the use of the DE4A technical system to have their evidence, e.g. diploma, required by the service transferred electronically from a trusted source in their home country satisfying applicable provisions of the SDGR and the GDPR. This way, students no longer have to search for the evidence themselves and fill out the required application forms.

Details of the services and the guidelines for participation can be found on the microsite of the Studying Abroad pilot

An additional cross-border diploma recognition service is expected to be launched in the coming weeks.

Service Interoperability Solutions Toolbox

Information Event from the Austrian Ministry of Finance on SDG Once Only and related topics.

In the technical work packages of DE4A, as well as in the technical task team and in DE4A participating organizations, different levels and types of specifications and documentation have been created during the project.

This process is fraught with the risk that project documentation becomes scattered, and structuring attempts are more often than not too late to be effective.

To prevent this, and as a part of WP2 Architecture Vision and Framework tasks, DE4A has produced a deliverable aimed at maintaining an orderly overview and thus maximizing the value of all the specifications, guidelines, etc. that work packages produce.

Moreover, this toolbox has been given the form of an online wiki, making publicly available relevant documentation such as DE4A interaction patterns, common components or pilots.

An Information Event from the Austrian Ministry of Finance on SDG Once Only and related topics was held online on 18.11.2022. The title of the event was "The realisation of the Once Only Principle in Austria and Europe". The event was attended by up to 125 participants, with no less than 90 participants taking part in each session.

One of these sessions was about EU-projects and initiatives and within this, DE4A was also explained (overall and status from AT side). In the invitation to the event DE4A was already mentioned: "The Austrian administration also continues to be involved in the European research project Digital Europe 4 All, in which 3 important use cases on the Once Only principle are being implemented."

Course: European Interoperability Framework (EIF) & Core Public Service Vocabulary (CPSV)

The international Hellenic University (IHU) has developed a free and open online course on the European Interoperability Framework (EIF) & Core Public Service Vocabulary (CPSV) as part of the dissemination of the project.

For the dissemination and exploitation of IHU expertise and for others to be able to delve into these technologies, IHU developed this course in such a way that can serve as a starting point for anyone who wishes to develop such services, while promoting the idea of using EU/EC made resources.

The main expertise and contribution of the IHU research team focuses on semantic web technology and interoperability, with the use of European standards and frameworks, such as EIF and CPSV-AP, whose adoption is crucial for the cross-border digital public services envisioned and piloted in the project. In DE4A, CPSV-AP is used as an important resource to construct vocabularies (WP3) and EIF guidelines are used in the architecture of the project (WP2), demonstrating their usage and value to interoperable, cross-border public services.

Our latest publications include:

DE4A and GLASS Projects collaborate to present at the
Open Identity Summit 2022 held at the Danish Technical University, in Lyngby, Denmark  - 
7th and 8th July 2022

The aim of the Open Identity Summit 2022 ( in Lyngby, Denmark, and hosted by the Danish Technical University, was to link practical experiences and requirements with academic innovations. Focus areas were Research and Applications in the area of Identity Management, Trust Services, Open Source, Internet of Things, Distributed Ledgers, Privacy and Cloud Computing.


Open standards and interfaces as well as open source technologies play a central role in the current identity management landscape as well as in emerging future scenarios in the area of electronic identification and trust services for electronic transactions. Reliable identity management is an essential building block for many applications and services such as innovative payment services, digital manufacturing, and other innovative applications in the area of e-health, e-government, distributed ledgers, cloud computing, data management for artificial intelligence, and the internet of things.


While there are already plenty of successful applications in which those techniques are applied to safeguard authenticity, integrity and confidentiality, there are still many closely related areas which demand further research. These include technical solutions that provide higher levels of transparency, intervenability and accountability.


GLASS and DE4A were jointly presented to explain their parallel approaches to the essential goal of understanding the credentials (evidences) being utilised and consumed in cross border actions which include multi-lingual and multi-context attributes. Vocabularies, syntax, ontologies were compared between the projects.

DE4A Project collaborates with the European DIGITAL SME Alliance to present the ‘Single Digital Market’ webinar
28th February 2022, CET: 10:00 to 11:15

EEMA is proud to announce that the DE4A project has collaborated with the European DIGITAL SME Alliance to present the ‘The Single Digital Market’ webinar.

EEMA is organizing a webinar where DE4A & the European DIGITAL SME Alliance will discuss the Digital Single Market and the importance of cross-border operations.

What will be discussed:

  • Challenges and opportunities for doing business across borders

  • DE4A and how it helps doing cross-border business operations

  • A DE4A ”Doing Business Abroad” Pilot Walk-through


  • Ard van der Heijden – Project Manager, DE4A Partner

  • Jon Shamah – EEMA Chairman, DE4A Partner

  • Alenka ZUZEK – DE4A Relationship Lead Government of Slovenia

  • Andrea Caccia – European DIGITAL SME Alliance, Senior Consultant & Project Manager, Standard and regulation compliance, Coordinator on Trust Services, eSeal, eDelivery & Blockchain

The recording of the webinar can be found below: