Data Flow¶

Credential Issuance¶

sequenceDiagram
    participant User
    participant Issuer as Issuance Service
    participant Furnisher as Data Furnisher
    participant VDR as GitHub VDR
    participant Harm as Harmonization
    participant Wallet

    User->>Issuer: Request Home Credential

    Issuer->>VDR: Fetch VCT (credential definition)
    VDR-->>Issuer: home-credential.vct.json
    Note over Issuer: VCT contains schema_uri,<br/>claims, acceptable_evidence

    Issuer->>Furnisher: Request property data
    Furnisher-->>Issuer: {assessed_val: 500000, full_address: "123 Main St"}

    Issuer->>Harm: Resolve evidence mappings
    Note over Harm: Maps furnisher:assessed_val → reso:AssessedValue
    Harm-->>Issuer: Evidence metadata + Entity info

    Issuer->>Issuer: Validate against schema (from VCT.schema_uri)
    Issuer->>Issuer: Build credential with evidence

    Issuer->>Wallet: Issue credential offer
    Wallet->>Wallet: Accept & store credential

    Wallet->>VDR: Fetch VCT (for rendering)
    Wallet->>Wallet: Render card with furnisher logo on back

Evidence in Credentials¶

When a credential is issued, evidence fields capture the data source:

{
  "@context": ["https://www.w3.org/ns/credentials/v2"],
  "type": ["VerifiableCredential", "HomeCredential"],
  "credentialSubject": {
    "AssessedValue": 500000,
    "UnparsedAddress": "123 Main St, Vancouver, BC"
  },
  "evidence": [
    {
      "type": "DataSourceEvidence",
      "verifier": "https://openpropertyassociation.ca",
      "sourceEntity": "https://openpropertyassociation.ca/credentials/entities/furnisher-example.json",
      "sourceName": "Example Data Furnisher",
      "verificationDate": "2024-12-11T10:30:00Z",
      "claimsCovered": ["AssessedValue", "UnparsedAddress"]
    }
  ]
}

The wallet uses this evidence to:

Display the furnisher logo on the credential back
Show verification provenance to relying parties

Multiple Evidence Sources¶

A single credential may combine data from multiple furnishers:

"evidence": [
  {
    "type": "DataSourceEvidence",
    "sourceEntity": "furnisher-a",
    "claimsCovered": ["givenName", "familyName"]
  },
  {
    "type": "DataSourceEvidence",
    "sourceEntity": "furnisher-b",
    "claimsCovered": ["AssessedValue", "UnparsedAddress"]
  }
]

The wallet would display logos from both furnishers on the credential back.

Future Considerations¶

Trust Registry Integration¶

Before accepting data from furnishers in an open ecosystem:

Verify the furnisher is authorized in the trust registry
Query trust registry to validate entity status
Prevent spoofing attacks

This is not needed now (closed ecosystem) but the architecture supports it.