Enabling secure, interoperable, and trustworthy urban digital twins

Modern digital infrastructures are evolving into decentralized and federated ecosystems that integrate data, services,and decisions across multiple domains and actors. In this context, Urban Digital Twins (UDTs) are emerging as dynamic platforms for simulating, analyzing, and governing urban information. By federating data and data sources from public authorities,private organizations and citizens under controlled sharing agreements, these systems enable secure and accountable data-driven planning and collaborative decision-making, ensuring that sensitive information is exchanged within well-defined trust and governance boundaries. However, their deployment still faces structural and systemic limitations, including semantic heterogeneity, data fragmentation, temporal inconsistency, and weak governance mechanisms, that hinder current implementations in managing heterogeneous models, preserving the evolution of spatial and administrative entities, and ensuring sovereignty and accountability across distributed infrastructures.These constraints limit the ability of UDTs to integrate and align data, processes, and governance rules across domains and administrative levels.The dissertation addresses these challenges from an architectural and methodological perspective, introducing a set of frameworks that together advance the interoperability, sovereignty, and trustworthiness of UDT. The research introduces two complementary integration architectures that address data fragmentation and interoperability across heterogeneous urban systems: a lightweight framework for modular service orchestration and scalable data exchange, and a semantic backbone that supports structured reasoning and cross-domain alignment. Building on the latter, a temporal data framework extends the semantic backbone with mechanisms for diachronic reconstruction and multi-temporal reasoning. To ensure sovereign and verifiable data exchangea decentralized data space model guarantees ownership,integrity and secure access control through decentralized identity and credential management aligned with the principles of Self-Sovereign Identity (SSI) and Findable, Accessible, Interoperable,and Reusable (FAIR) data. Finally, a federated process governance framework introduces mechanisms for tracing contributions, estimating influence,and mitigating adversarial updates, ensuring transparency and accountability in distributed decision-making. Collectively,these contributions provide the building blocks for interoperable, temporally aware,and trustworthy UDT ecosystems