Replace PE Schema with Type

[David W Chadwick]

Issue 213 in the DIF PE spec (https://github.com/decentralized-identity/presentation-exchange/issues/213) suggests to replace the schema property with the type property. This parallel issue is raised here in order to track the DIF PE issue and to support its resolution.

[Nat Sakimura]

It is a placeholder just in case DIF did not address it.

[Kristina Yasuda]

There is a proposal in DIF to remove `schema` field all together to use JSON Path to point where to find the shape of data being requested (credentialSchema or type fields of VCs)

Here are examples: https://hackmd.io/0tmo69rrRkeiryDZE_5waQ

I think this is problematic from interop/security perspective because path is not bound to credential format.

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[Daniel Buchner]

We might want to look at an even simpler route of just using field evaluation to allow a Verifier to query whatever part of the candidate credential inputs they want to determine whether it is of the right type/schema. This would be nice, because no new mechanics would need to be added, and we could remove the one-off type/schema property altogether.

[David W Chadwick]

Daniel, how is you suggestion different to Kristina’s?

Kristina, doesn’t your objection apply to every constraint in the input descriptor?

[Daniel Buchner]

Kristina: you can make the path account for the format, or, as Torsten requested (and we added in a PR this week to the 2.0 spec draft) you can separate out your Input Descriptors with per-descriptor format declarations, if you don’t like to use paths to account for them.

[Kristina Yasuda]

suggest we close this, since agreement was not reached on this in DIF-OIDF calls and PEv2

• renames the parameter to types from `schema`
• moves type/schema parameter from input_descriptors into input_descriptors.constraints
• mandates passing requested type by reference using JSONPath as opposed to by reference as it was in PEv1

Now:

"input_descriptors": [
 "constraints": {
          "types": [
            {
              "path": ["$.credentialSchema.id", "$.vc.credentialSchema.id"],
              "filter": {
                "type": "string",
                "pattern": "https://bank-schemas.org/1.0.0/accounts.json|https://bank-schemas.org/2.0.0/accounts.json"
              }
            }
          ]
 }
]

Before

"input_descriptors": [
      {
        "id": "banking_input_1",
        "schema": [
          {
            "uri": "https://bank-schemas.org/1.0.0/accounts.json"
          },
          {
            "uri": "https://bank-schemas.org/2.0.0/accounts.json"
          }
        ]
      }
}

‌

[David W Chadwick]

Agreed that this can be closed as this particular issue has been resolved. (However it does raise another issue that PE has now duplicated the way that requesting a specific type of VC can be performed: firstly in this new types parameter, and secondly in the original constraints formulation.)

[Kristina Yasuda]

resolving since PE v2 moved on to using neither schema or type, but JSON.Path