From Planning Support Systems to Urban Digital Twins: A Decision-Driven Framework for Participatory Spatial Planning
Purpose: The paper develops a conceptual framework in which an urban digital twin (UDT) is derived from planning decisions and the statutory planning procedure rather than from a predefined technical architecture. The Polish municipal general plan serves as the procedural case. Design/Methodology/Approach: The methodological approach combines conceptual framework analysis with an integrative review of participatory planning, planning support systems (PSS), public participation GIS (PPGIS) and UDT literature, alongside a legal-procedural analysis of the Polish general-plan procedure. Plausibility is examined ex ante through a scenario on accessibility standards in Szczecin. Findings: The framework identifies three conditions that characterise decisions particularly suited to participatory UDT support, four functional domains and six traceable knowledge flows linking local knowledge, analysis, deliberation and formal decisions. It proposes decision-proportional fidelity: representational detail and technological complexity should be matched to the requirements of the planning decision. For accessibility standards, a periodically updated digital shadow may suffice. Practical Implications: Municipalities can start with measurable and contested decisions, use geo-questionnaires as provenance-aware inputs to the knowledge base and keep a traceable register of contributions, revisions and responses. Staged implementation based largely on public data may lower the entry threshold. Originality/Value: The framework shifts UDT conceptualisation from technical architecture towards the organisation of planning decisions, knowledge flows and accountability.