Reference Architecture Views & Viewpoints ========================================= The European Interoperability Reference Architecture organises its building blocks and their relationships through four complementary architectural views, known as the LOST views: Legal, Organisational, Semantic, and Technical. These views provide a structured approach to addressing the multidimensional nature of interoperability in European public administrations, ensuring that digital services can effectively interact across organisational, jurisdictional, and technical boundaries. Each view addresses a distinct aspect of interoperability challenges whilst maintaining coherence with the overall architecture. As a summary of what is later described: the Legal view encompasses regulatory requirements, governance frameworks, and compliance considerations that enable lawful cross-border data exchange. The Organisational view defines the business processes, roles, and collaborative arrangements necessary for coordinated service delivery. The Semantic view ensures shared understanding of information through standardised vocabularies, data models, and agreed meanings. The Technical view addresses the infrastructure, applications, and technical standards that enable system-to-system communication and data exchange. Aside from the views, in this section the concept of viewpoints and how are they used in the Reference Architecture will be included, making an explicit separation between both. Views ----- As introduced, EIRA is composed of the four views defined in EIF (LOST): Legal, Organisational, Semantic and Technical. Each view represents a perspective focusing on a particular dimension of interoperability and encompasses the building blocks relevant to that dimension. Legal view ~~~~~~~~~~ The **Legal view** addresses the legislative and regulatory framework within which digital public services must operate, capturing legal constraints, compliance obligations, and the legal instruments that enable or constrain interoperability. This view encompasses ABBs related to legislation, regulations, agreements, and legal frameworks that govern data sharing, service provision, cross-border cooperation, and citizen rights. Legal interoperability ensures that organizations can exchange information and collaborate across jurisdictional boundaries while respecting different legal frameworks and meeting mandatory compliance requirements. The Legal view includes instruments such as data protection regulations including GDPR, sector-specific legislation, cross-border legal agreements enabling mutual recognition of documents and decisions, accessibility requirements, and intellectual property constraints. EIRA provides several viewpoints that offer a more focused and detailed lens on the legal building blocs as well as how they are combined with the remaining views in EIRA. Organisational view ~~~~~~~~~~~~~~~~~~~ The **Organisational View** models how organizations define roles and responsibilities, establish governance mechanisms, and collaborate to deliver digital public services. This view models Digital Business Capabilities representing what an organization must be able achieve to fulfil its mission, Digital Public Services as the externally visible service offerings delivered to citizens and businesses, and Business Information representing the critical data assets that flow through business processes. Organisational interoperability addresses alignment of business processes, information lifecycles, and administrative procedures across organizational boundaries, enabling different entities to work together effectively even when they have different internal structures and mandates. Semantic view ~~~~~~~~~~~~~ The **Semantic View** ensures that information exchanged between systems and organizations is interpreted consistently and accurately, addressing the meaning, structure, and relationships of data. Interoperability is achieved through shared data models, controlled vocabularies, domain ontologies, metadata schemas, and data quality specifications that enable different systems to understand the information they exchange regardless of differences in internal representations. To address Semantic Governance, this view includes elements defining policies for the security and privacy of the information and to govern Master Data, Open Data – including compliance with the FAIR principles: Findable, Accessible, Interoperable, and Reusable – and Portability. Technical view, Application and Infrastructure ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The **Technical view** is composed by two views, the Application and Infrastructure. The purpose is to better separate concepts. Application view ^^^^^^^^^^^^^^^^ The **Application layer** focuses on application-level capabilities that makes solutions interoperable by design. This layer encompasses Application Components that implement business functionality, Application Services defining the functionality exposed by applications to other applications or users through well-defined interfaces, Application Interfaces specifying the interaction with Humans or Machine-to-Machine and API specifications. This layer also includes the platform enablers typically offered as shared services. Identification and access enabler which encompass the authorisation and authentication of users, systems and services. Security enablers that support the implementation and management of security controls. Trust Enablers required for cross border transactions (e-signatures and e-seals, Registered Electronic Delivery, integrity verification realised by Trust Service Provisioning), Data Exchange services, and other application layer capabilities such as Data Management (ETL, persistence, virtualisation, quality, publication, metadata management, e archiving), Analytics/AI, Translation, Schedule/Agenda Management, and Dataspace Enablers. Infrastructure view ^^^^^^^^^^^^^^^^^^^ The **Infrastructure layer** incorporates technology platforms that supports and enables interoperability between Digital Public Services. This layer includes Technology Services representing infrastructure capabilities such as hosting platforms, networks, and storage. Communication Infrastructure providing the networks and connectivity enabling information exchange between systems, and Security Infrastructure delivering authentication, authorization, encryption, firewalls, and other protective mechanisms. Infrastructure interoperability ensures that applications can communicate and exchange data reliably, securely, and efficiently regardless of differences in underlying technology platforms, hosting models including on-premises, cloud, and hybrid approaches, network protocols and connectivity solutions, and security mechanisms and trust frameworks. These elements support application-level interoperability through infrastructure capabilities, identify infrastructure dependencies and constraints, plan for scalability, resilience, and performance. Viewpoints ---------- In addition to the four views defined in EIF, EIRA includes a set of viewpoints to address a specific concern referent to an interoperability domain. Each viewpoint combines the relevant elements from the four views to a provide a focused lens. Interoperability Dimensions viewpoints ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ These viewpoints are used to describe the three interoperability dimensions and how the different architecture building blocks that enable the different Interoperability Dimensions (Governance, Structural, and Behavioural). The **Interoperability Structural viewpoint** models the compositional architecture of digital public services, focusing on the components and building blocks that form the structural foundation of interoperable solutions. This viewpoint presents Architecture Building Blocks organised according to their role in the overall system structure, emphasising reusability and component sharing as key principles of interoperability by design. The **Interoperability Behavioural viewpoint** models the dynamic aspects of digital public services, focusing on how Architecture Building Blocks interact through the exchange of data, information, and knowledge with their environment. The **Interoperability Governance viewpoint** models the interoperability coordination and governance across organisations and domains, focusing on the decisions and structures to ensure the compliance of all participants with the stablished frameworks and policies. It features the instruments needed to plan, implement and monitor interoperability efforts without diving into operational details. Other viewpoints defined in EIRA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Apart from the viewpoints mentioned above, the Reference Architecture defines additional sets of viewpoints, which are focused on provide additional information on key aspects such as Privacy or Security, as well as, providing the high-level definition of the main elements and its relationships in the design of a solution. The **Interoperability Privacy viewpoint** is dedicated to the privacy aspect of interoperability by introducing privacy into the architecture ensuring that any solution respects the data protection obligations. Here are highlighted the ABBs relevant to designing and evaluating that an architecture complies with the privacy principles and legal requirements such as the General Data Protection Regulation (GDPR). This is crucial for public services to enforce the confidentiality, authenticity, integrity and non-repudiation of information provided by citizens and businesses. The **Interoperability Security viewpoint** focuses on the security and trust aspects of interoperability, ensuring that exchanges between citizens and businesses and public administration are protected and occur in a trustworthy environment. This viewpoint encompasses frameworks, policies and mechanisms that support a secure-by-design approach to designing public services that implement confidentiality, authenticity, integrity and non-repudiation of information it handles and exchanges. The **High Level viewpoint** provides an executive overview of the architecture, presenting the key building blocks that connect and integrate the four LOST views. The building blocks featured in this viewpoint act as integration points across the architecture, enabling stakeholders to trace relationships and dependencies between different interoperability concerns. Views and viewpoints, differences and purposes ---------------------------------------------- In alignment with ArchiMate, views and viewpoints in EIRA and eGovERA serve different purposes. While a view is addressing more than one interoperability aspect, a viewpoint depicts, and frames detailed aspects expressed in the views. Viewpoints are a means to focus on particular aspects and layers of the architecture.