About the Document
The document is the MIMs Plus Specification 8.0, dated 30 June 2025, a technical specification on minimal interoperability mechanisms (MIMs) for smart city solutions. It is published under the Living-in.eu site and is licensed under CC BY-NC 4.0 on its cover page, while section 1.3 states a CC BY-SA 4.0 licence. The text does not name individual authors; it refers to working groups, including the MIM3 and MIM8 working groups.
Purpose and Audience
- The MIMs Plus enable "a minimal but sufficient level of interoperability for data, systems, and services" in smart city contexts.
- The intended audiences are solution providers seeking interoperable solutions and procurers seeking future-proof solutions that allow cost-effective integration.
Framework Structure
The framework has two categories. Foundational MIMs cover the typical data journey: MIM0 Accessing Data, MIM2 Representing Data, MIM3 Exchanging Data and MIM1 Interlinking Data. Application-specific MIMs address particular domains, including MIM6 Securing Data, MIM4 Personal Data, MIM7 Geospatial Data and MIM8 Local Digital Twins. Each MIM follows the structure of the ITU Y.4505 standard: objectives, capabilities, requirements, mechanisms, interoperability guidance and conformance testing.
Key Requirements
- MIM1 requires every entity to have a unique identifier and a way to retrieve information about it.
- MIM2 requires explicit, documented data models, based where possible on standards such as ISO/IEC 5087, SAREF and NGSI-LD.
- MIM3 sets governance rules, terms and conditions, compliance validation and data discovery for data-sharing ecosystems.
- MIM7 recommends OGC standards, with GeoJSON and CityJSON preferred for API-based geospatial encoding.
Security and Personal Data
MIM6 focuses on secure data transfer, with capabilities for access control, unaltered transmitted data and verified sources, referencing ISO 27001:2022 and IEC 62443. MIM4 aims to let individuals control which data they share with providers, noting a fragmented market split between the MyData and Solid networks.
Local Digital Twins and Use Cases
MIM8 defines a Local (or Urban) Digital Twin as a digital representation of physical assets or processes that supports visualisation, analysis, simulation and decision-making. It classifies twins as Awareness, Experimental, Predictive or Intelligent. Section 10 lists use cases from Brussels, Cartagena, Espoo, Leuven, Madrid, Sofia and Valencia, each with a chosen category and an interoperability issue.
Why It Matters for Smart City Interoperability
The specification is presented as guidance for cities and communities building interoperable local data ecosystems, and for the solution providers and procurers who serve them.