Interoperable smart city transformation: Insights from European data space for smart communities

The European Data Space for Smart Communities (DS4SSCC) is a flagship initiative demonstrating how interoperable, cross-domain data infrastructures can drive smart city transformation in Europe. Yet achieving interoperability across legal, organisational, semantic, and technical layers remains difficult for local governments constrained by legacy systems, rigid procurement, and fragmented ICT landscapes. This paper examines how interoperability is operationalised within DS4SSCC through the Minimal Interoperability Mechanisms (MIMs) Plus framework. Using a qualitative case study approach- combining document analysis, stakeholder survey data, and workshop insights from the DS4SSCC Preparatory Action-the study analyses how governance structures, technical standards, and procurement mechanisms interact to enable cross-domain collaboration. The findings identify five key enablers of interoperability-by-design: modular data architectures, shared governance, lightweight semantic alignment, interoperability clauses in procurement, and capacity building. Foundational MIMs (Accessing, Representing, Interlinking, Securing, and Sharing Data) underpin DS4SSCC's core building blocks, while application-specific MIMs (Personal Data, Geospatial, Interoperable AI, and Local Digital Twin) support more complex, cross-domain use cases. Persistent challenges include uneven capacity, vendor lock-in, and variable conformance maturity. The paper concludes that MIMs Plus translates the four layers of the European Interoperability Framework into actionable mechanisms, positioning interoperability as a continuous governance capability essential for scalable and trustworthy data spaces.