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• Common Data Models: Using standardised attributes, such as those defined by the W3C Verifiable Credentials Data Model, OpenID4VC etc, to ensure a “date of birth” or a "person identifier" field is interpreted the same way across systems.
• Ontology Alignment: Agreeing on the meaning of terms, such as what constitutes a “verified identity” or a “trusted issuer,” to avoid miscommunication.
• Interoperable Formats: Supporting formats like JSON-LD for credentials to ensure data can be read and processed by different identity wallets.
• Schemas for understanding credentials: E.g. ELM, OpenBadge, EMREX, ELMO, but also different isolated schemas at the national level. Need to interoperate with existing schemata
• Profiles:
  • Need for (transport) protocol interop profile, e.g. see HAIP (High Assurance Interop Profile) or something more lightweight like DIIP (Decentralised Identity Interop Profile).
  • Need for trust profile (e.g. OpenID for Research and Education (OpenID4RE) Project or OpenID Federation for Wallets architecture)
  • National profiles (e.g. based on ELM)

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End-to-end Interoperability

Technical interoperability ensures that the underlying technologies of identity wallets and distributed identity systems can work together. This can be broken down into several subcategories (see also Educational interoperability by SURF):

Users & Services

• Ensuring that identity wallets provide a consistent user experience across different platforms (e.g., mobile apps, web interfaces).
• Supporting seamless interaction between users and services, such as using a single identity wallet to log into both a government portal and an R&E service

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