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Semantic interoperability ensures that different systems interpret and understand identity data consistently. This involves:

• Common Data Models: Using standardised attributesA data model defines the structure and relationships of data elements, providing a framework for how identity information is represented and exchanged. Using standardised attributes, such as those defined by the W3C Verifiable Credentials Data Model, OpenID4VC etc, to ensure ensures a “date of birth” or a "person identifier" field is interpreted the same way are consistently structured and interpreted 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. Schemas define the specific structure and required attributes for credentials, such as those used in ELM, OpenBadge, EMREX, ELMO, but also different isolated schemas at the national level. Need to interoperate with existing schemataThese schemas must be interoperable to allow credentials issued in one system to be understood and verified in another. For example, a schema for a digital diploma must specify fields like issuer, recipient, and issuance date in a standardised way.
• Profiles: Profiles are sets of specifications or configurations that define how standards and protocols are implemented to achieve interoperability.
  • A transport interoperability protocol, such as
  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)., ensures consistent communication between systems.
  • Trust profiles, such as the Need for trust profile (e.g. OpenID for Research and Education (OpenID4RE) Project or or  the OpenID Federation for Wallets architecture), establish rules for trust relationships.
  • National profiles (e.g. based on ELM), like those bases on ELM, may further specify local requirements for credentials formats and verification processes.

End-to-end Interoperability

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