A European platform for open local digital twins

Member State LDT Appstore

What does a Member State LDT Appstore consist of?

A Member State LDT Appstore consists of interrelated building blocks: a catalog layer, an interoperability and quality layer, a governance and trust layer, and a federation and integration layer—supported by operational processes.

1) Catalog layer: what you publish and how it can be found

Asset types (supply)

  • Data products: datasets and data APIs (incl. geodata)
  • Service products: data services and (geo)web services
  • Model products: simulation/optimization/AI models as a service
  • Visualization & interaction: dashboards, 3D viewers, scenario boards
  • Workflows/recipes: repeatable chains/pipelines that combine components
  • Registries & vocabularies: concept lists, code lists, mappings, reference lists

Metadata model (machine-readable)

  • Separation between catalog record (lifecycle/governance) and cataloged resource (the item itself).
  • Based on DCAT/DCAT-AP; for geo often GeoDCAT-AP/INSPIRE alignment.

Product page/UX

  • Translates metadata into decision information: “what can I do with this?”, conditions, restrictions, contact/support, dependencies, and implementation instructions.
2) Interoperability and quality layer: from “findable” to “usable”
  • Conformance & test results: Automate checks (e.g., OGC API conformance classes) and record results as trust signals.
  • Semantic interoperability: shared vocabularies, mappings, and reference registers so that indicators and definitions are consistent.
  • Version control & lifecycle: status, changelog, deprecation policy, dependencies, and compatibility of workflows/services.
  • Data quality profiles (completeness, timeliness, accuracy)
  • Provenance/lineage (origin, processing, validations)
  • Reproducibility of models and scenarios (inputs, parameter sets, reference cases)
3) Governance and trust layer: who is allowed to do what, under which rules
  • Roles & responsibilities: at least Provider, Curator, Steward, Operator, Consumer, including incident, escalation, and deprecation processes.
  • Assurance levels (tiers), proportional and growable:
    • Tier 0: self-declared + basic validations
    • Tier 1: curated + basic conformance tests + provenance/license clear
    • Tier 2: independently verified + security posture + reproducibility + (where relevant) risk documentation
  • Legal & policy: licenses/user rights, access classes (open/registered/contractual), privacy/GDPR artifacts where necessary, and for AI: transparency and risk documentation.
  • Access and authorization policies (RBAC/ABAC), logging, and audit trail
  • Security baseline (encryption, key management, incident response)
  • Complaints and objections route and governance for changes in the rules of the game
4) Federation and integration layer: nationally usable, European scalable
  • Federation patterns: harvesting, distributed query, or hybrid—for “no-wrong-door discovery” (local/national/EU).
  • Trust/federation services (connection with data spaces): identity/attestation, policy enforcement, logging/auditability (often via existing building blocks instead of "in the App Store itself").
  • EU LDT Toolbox Relationship: The App Store serves as a trusted catalog layer for describing and discovering toolbox-aligned components, including reference implementations and workflows.
  • Linking to national registers and identifications (e.g. object IDs)
  • API gateway/policy gateway voor uniforme toegang en throttling
  • Cross-border metadata harmonization (multilingualism, minimum metadata set)
5) Operational processes: so that it works as an ecosystem
  • Onboarding pipeline: pre-submission guidance → automated metadata validation → curator review (Tier 1+) → conformance testing → publication → monitoring/feedback.
  • Monitoring & feedback loops: uptime/link checks, user experiences, issue reporting and KPIs (such as time-to-integrate and reuse rate)
  • Change management (version policy, impact analysis, communication)
  • Adoptie- en communityproces (handleidingen, voorbeeld-implementaties, training)
  • Portfolio management (prioritization of assets and gaps based on national tasks)

In summary: one shared reality, scalably organised

The Member State LDT Appstore enables reuse by combining discoverability, comparability, and trust. TwinLink.eu ensures the prerequisite: fair rules and governance that allow regional parties to manage a single, shared reality. Once this foundation is in place, Regional SPoT and Common Workspace make it practical—creating an ecosystem in which chain partners can collaborate based on the same reliable information and integrated processes.