1. Introduction

The European public sector is undergoing a profound digital transformation driven by increasing societal expectations, cross-border service demands, rapid technological change, and an evolving European regulatory landscape. Public administrations are now required to design, implement, and operate interoperable, high-quality and trustworthy digital public services, while ensuring compliance with EU legislation such as the Interoperable Europe Act, the GDPR, the Open Data Directive, the Data Governance Act, the Data Act, and domain-specific legal frameworks.

In this context, interoperability has become a foundational capability for modern public administrations. It enables administration-wide and cross-border collaboration, promotes reuse of solutions and building blocks, reduces fragmentation and vendor-lock-in, and ensures that digital public services can work together seamlessly to deliver public value. Interoperability is not only a technical requirement, but a policy, organisational and semantic capability that must be built into the full lifecycle of digital public services.

To support this effort, the European Commission, through the Interoperable Europe initiative, provides a set of reference architectures, methodological frameworks, and reusable resources that guide Member States and EU institutions in the design and implementation of interoperable solutions. Among these, two key instruments play a central role:

  • The European Interoperability Reference Architecture (EIRA): it is a formal meta concept, level 1 granularity vocabulary of Architecture Building Blocks (ABBs) expressed in ArchiMate, structured along the Legal, Organisational, Semantic and Technical (LOST) interoperability views defined by the European Interoperability Framework (EIF). EIRA supports the analysis of a digital public service requirements use case and the design of a digital public service use case enabling the identification of reusable solution building blocks.

  • The eGovernment European Reference Architecture (eGovERA): it is a formal level 2 and further granularity vocabulary, based on and extending EIRA. eGovERA includes architecture patterns, and it supports analysis and design of a digital public service use cases.

This specification covers EIRA as the level 1 granularity of the European Interoperability Reference Architecture and eGovERA as the level 2 and further level of granularity of the European Interoperability Reference Architecture. For the sake of simplification, the term European Interoperability Reference Architecture, EIRA, covers also eGovERA. When appropriate in this document eGovERA aspects of the specification will be explicited. EIRA and eGovERA provide a coherent, architecture-driven and model-based approach sypporting the implementation life-cycle of interoperable, high-quality digital public services.

1.1. Purpose of this Specification

This specification documents the European Interoperability Reference Architecture, eGovERA included. It provides:

  • A harmonised conceptual and methodological foundation aligning EIRA and eGovERA.

  • A clear description of the roles, use cases, and value proposition of each reference architecture.

  • A detailed presentation of the interoperability views, building blocks, architecture patterns, and modelling conventions.

Guidance for conformance, governance, quality assurance, and lifecycle management of digital public service solutions.

1.2. Scope

This specification defines the European Interoperability Reference Architecture, EIRA , and establishes a unified architectural and methodological framework to support the analysis, design and governance of interoperable digital public services in the European Union public administrations.

The scope of this specification includes:

  • A harmonised conceptual foundation describing the principles, architecture ontology, modelling conventions and interoperability views (Legal, Organisational, Semantic and Technical) that underpin the reference architectures.

  • The definition and structuring of Architecture Building Blocks (ABBs) and their transformation into Solution Building Blocks (SBBs) to support the full lifecycle of digital public service engineering.

  • The methodological alignment between analysis and design, including decomposition principles, traceability rules, architecture patterns and interoperability considerations.

  • Guidance for role-based use of the reference architectures, enabling different professional profiles to navigate the models according to their domain concerns.

  • Conformance and governance provisions, including interoperability assessment, model quality requirements, and architecture-driven decision-support for digital public service implementation.

The following aspects are outside the scope of this specification:

  • Domain-specific reference architectures, although the present specification provides the common domain-agnostic foundation on which they may be based.

  • Detailed implementation procedures, procurement templates and operational manuals.

  • Tool-specific modelling instructions beyond the use of ArchiMate as the prescribed architecture ontology.

  • Organisation-specific governance arrangements, except where directly required to fulfil EU-level interoperability principles.

1.3. Target Audience

This specification is designed for:

  • Policy Makers & Digital Strategy Leaders.

  • Enterprise & Solution Architects.

  • Portfolio & Programme Managers.

  • Solution Providers & Project Teams.

  • Academia & Training Organisations.

1.4. Relationship to Other Frameworks and Standards

The Reference Architecture aligns with, and draws inspiration from:

  • Interoperability frameworks (e.g., EIF, national frameworks).

  • Enterprise architecture methodologies (e.g., TOGAF(c)).

  • Modelling standards (e.g., ArchiMate(c) ).

  • Technical specifications (e.g., W3C standards for semantic and web interoperability).

1.5. Document Conventions and Terminology

  • Normative Text: MUST, MUST NOT, SHOULD, SHOULD NOT, MAY (RFC 2119).

  • Non-Normative Text: Guidance and recommendations (not binding).

  • Reference Architecture (RA): A standardised architectural framework.

  • Architecture Building Block (ABB): Abstract, reusable element.

  • Solution Building Block (SBB): Concrete implementation of ABBs.

  • Interoperability Views: Legal, Organisational, Semantic, Technical.