The Interoperability Structural Viewpoint defines the structural composition of digital solutions in terms of reusable and shareable architectural building blocks that enable interoperability by design. This viewpoint focuses on the static arrangement and relationships of components, services, and enablers that can be reused or shared across Digital Public Services, organisations, or domains. It supports structural interoperability by promoting modularity, and consistency. By making reuse and sharing explicit at architecture level, the Interoperability Structural Viewpoint facilitates efficient solution design, reduces duplication, and supports cross-border and cross-sector interoperability within the European public administration landscape.