Credential definitions are written to the ledger by the issuer of a credential—every kind of credential to be issued needs its own unique credential definition. A credential definition can reference claim types from a single schema or from different schemas. For example, there could be a single Driver’s License schema that is shared between all 50 states in the USA, however each state must have its own credential definition for its own driver’s license credential. There is no limit to the number of credentials that can be issued from a single credential definition, and there is no cost beyond the one-time registration fee