DTG Credential Categories

The DTG specification organizes its credential types into four descriptive (non-normative) functional categories. These categories don’t appear in credential schemas — they’re a conceptual framework for understanding what each credential type does in the trust graph.

The Four Categories

Edge Credentials

Establish relationships between existing entities (nodes) in the graph. Both edge credential types are bidirectional — a complete edge requires a pair, one from each side.

• VMC (Membership) — a membership edge between an entity and a community, verified through a bi-directional pair of VMCs
• VRC (Relationship) — a peer-to-peer relationship edge between two entities, verified through a bi-directional pair of VRCs

Invitation Credentials

Bootstrap new participants into communities.

• VIC (Invitation) — authorizes onboarding of a new member into a VTC or VTN

Annotation Credentials

Attach additional data to existing graph structure without creating new edges.

• VPC (Persona) — links a persona identity to an existing relationship
• VEC (Endorsement) — endorses skills or reputation of an existing member
• VWC (Witness) — third-party attestation that an edge (VRC exchange) actually occurred

Verifiable Data Structures (VDS)

Structured data exchange — not technically DTG credentials.

• RCard (Relationship Card) — human-readable contact information (vCard/jCard per RFC 7095)

Note: RCard does not include DTGCredential in its W3C type array — its type is ["VerifiableCredential", "RelationshipCard"]. It is a Verifiable Data Structure, not a credential in the DTG sense.

The Formal Type Hierarchy

All DTG credentials share a common W3C type hierarchy:

VerifiableCredential
└── DTGCredential
    ├── MembershipCredential (VMC)
    ├── RelationshipCredential (VRC)
    ├── InvitationCredential (VIC)
    ├── PersonaCredential (VPC)
    ├── EndorsementCredential (VEC)
    └── WitnessCredential (VWC)

VerifiableCredential
└── RelationshipCard (RCard)  ← NOT a DTGCredential

The only abstract parent in the formal hierarchy is DTGCredential. The four descriptive categories above are for human understanding only.

ZKP Anchor Points

Both Edge Credentials are anchors for ZKP constructions defined in the spec:

• The VRC anchors a pairwise ZKP — available between any two VRC holders, no shared community required, useful for selectively disclosing P-DIDs while hiding R-DIDs.
• The VMC anchors a community-anchored ZKP — requires both parties to hold VMCs from the same community, carries that community’s governance assurance (including personhood when applicable) into the proof.

The spec recommends ZKP presentation by default for all DTG credentials.

See also: zero-knowledge-proofs, dtg-credentials-overview, decentralized-trust-graph