How are credential copies issued?

[danielfett]

Originally posted by @danielfett in https://github.com/openid/OpenID4VCI/pull/65#discussion_r1372116662

The relationship currently described is that in any issuance process, multiple "types" of credentials can be issued (*), and for each "type" there can be multiple instances. An instance is described as "contains different claim values or different subset of claims within the claimset identified by the Credential type"

(issuance process) --- 1:n --- (credential definition*) --- 1:m --- (credential instance)

How is the relationship to batch issuance for unlinkability as suggested in SD-JWT? Is this already covered or should there be a separate mechanism for that? I.e., to have something like this for k copies of the same credential:

(issuance process) --- 1:n --- (credential definition*) --- 1:m --- (credential instance) --- 1:k --- (credential instance copy)

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(*) entry in the credentials_supported Credential Issuer metadata - I added a comment suggesting to find a good term for this to use instead of credential type.