The main objective of The “Once-Only” Principle Project (TOOP) is to explore and demonstrate the functionality of the “once-only” principle through sustainable multiple pilots, using a federated architecture on a cross-border collaborative pan-European scale in order to identify drivers and barriers and to provide a basis for future implementation and wider use. The functionality of the “Once-Only” Principle (OOP) is explored and demonstrated in three pilots: Cross-border eServices for Business Mobility, Updating Connected Company Data and Online Ship and Crew Certificates. The methodological approach of TOOP is based on an exploratory and agile pilot life-cycle approach to sustainable multiple cross-border pilots of e-services, the planning and implementation of which is supported by the development of a generic federated architecture and building blocks, the identification and mitigation of barriers (including the legal issues) and the evaluation of the results, with pro-active dissemination and sustainable exploitation of the results throughout the project. TOOP’s main technological innovation is a generic federated OOP architecture that supports the interconnection and interoperability of national registries at the EU level. The pilots planned are ambitious as they contain product, service and organisational innovations not existing in the market today and provide a basis for recommendations for future implementations and the wider use of the OOP.


Duration 01/01/2017 - 31/05/2021
Funding EU
Program Horizon 2020
Logo - European Union

Department for E-Governance and Administration

Center for E-Governance

Principle investigator for the project (University for Continuing Education Krems) Assoz. Prof. Dipl.-Ing.(FH) Dr. Thomas Lampoltshammer, M.A. MSc MBA
Project members


Lampoltshammer, T.J.; John, K.; Helger, P.; Piswanger, C-M. (2019). Connectathons - A Sustainable Path Towards Development in European Large-Scale Pilots. In: Virkar, S.; Glassey, O.; Janssen, M.; Parycek, P.; Polini, A.; Re, B.; Reichstädter, P.; Scholl, H.J.; Tambouris, E., Proceedings of Ongoing Research, Practitioners, Posters, Workshops, and Projects of the International Conference EGOV-CeDEM-ePart 2019: 207-214, CEUR, Del Tronto, Italy


Benefits and barriers of the OOP implementation in the BRs domain (Workshop)

The 'Once-Only' & Business Registers Workshop, EBRA Conference 2019, Tallinn, Estland, 05/06/2019


ADV Verwaltungsinformatik 2018 - Verringerung des Digitalisierungsgaps innerhalb der Verwaltung; Vienna, 15/11/2018

Chancen und Risiken der digitalen Datenverwaltung und Datennutzung in der öffentlichen Verwaltung (Podium)

Netzwerkveranstaltung 2018 der Geschäftsstelle E-Government Schweiz, 20/09/2018

Umsetzung des Once-Only-Prinzips in der Europäischen Union (Invited Talk)

Netzwerkveranstaltung 2018 der Geschäftsstelle E-Government Schweiz, 20/09/2018

TOOP - The Once-Only Principle Project (Workshop)

Innovation-Lab Symposium 2018, GovLabAustria, Donau-Universität Krems, Krems, Austria, 18/01/2018

TOOP Governance

"Once Only Principle in Europe" - TOOP project dissemination event in Austria, Federal Computing Center, 02/11/2017

Back to top