Reference Architecture

DE4A developed a multi-pattern architecture for eGovernment interoperability with a focus on digital-by-default procedures for citizens and businesses and the full implementation of the Once-Only Principle. It is developed with a clear focus on providing direction to the DE4A Pilots as part of the public deliverables D2.4 Project Start Architecture (PSA) - First iteration and D2.5 Project Start Architecture (PSA) - second iteration. Most important inputs to the PSA are the Architecture Framework, the detailed requirements of the DE4A Pilots and an analysis of the legal requirements of Article 14 of the Regulation (EU) 2018/1724 establishing a single digital gateway to provide access to information, to procedures and to assistance and problem-solving service (SDGR). These insights where condensed into a list of Interdisciplinary Questions that provided the structure to define underlying working assumptions per interaction pattern.

The PSA recognizes five distinct Reference Interaction Patterns:

• Intermediation Pattern
• User-supported Intermediation Pattern
• Verifiable Credentials Pattern
• Lookup Pattern
• Subscription and Notification Pattern

The design of the Intermediation Pattern took the Single Digital Gateway (SDG) Once-Only Technical System High Level Architecture (HLA) and insights gained from the TOOP Reference Architecture as starting point and was instrumental in uncovering implicit assumptions (i.e. working hypotheses) concerning the fundamental, Interdisciplinary Questions in context of cross-border exchange of evidence. The User-supported Intermediation Pattern can relax some of these hypotheses by introducing a direct interaction between the User and the Data Provider. These two patterns fall in the Time Horizon t=2 (~end 2023), whereas the third pattern, the Verifiable Credentials Pattern opens a perspective to a potential future solution (t=3) and investigates the transformative impact of new blockchain technologies. These three pattern are all concerned with the exchange of evidence in the direct context of the user-interaction in an eProcedure.

Two further patterns introduce exchange of information between public authorities at a later point in time and without direct user-interaction. The Subscription and Notification Pattern provides the possibility to the Data Owner to receive a signal if the status of the user (i.e. the company) changes over time in a way that is significant for the ongoing service provided (i.e. subsidy). The Lookup Pattern then allows the DO to retrieve an updated version of a previously exchanged evidence.

The DE4A Reference Architecture is based on the Architecture Metamodel described in deliverable D2.1 Architecture Framework and applies the definitions and description language from ArchiMate and BPMN. The DE4A Architecture Framework defines five architecture Time Horizons staring from the pre-SDG baseline (t=0, ~2019) and reaching to a long-term vision (t=4, ~2030+) in order to place different developments in context. More detail on the Architecture Framework is available in the public deliverable D2.1 Architecture Framework.

DE4A also maintains an Architecture Log that keeps track of deviations from DE4A principles and the reference architecture.