Re: VC Evidence Discussion

Rebase also used `evidence` for proof of verification:
https://github.com/spruceid/tzprofiles. We are also thinking to use
`evidence` for VPs to express additional info needed for holder binding.

On Fri, Apr 8, 2022 at 12:04 PM Joosten, H.J.M. (Rieks) <
rieks.joosten@tno.nl> wrote:

> Let’s stick to what the VC data model 1.1. says about the intention of the
> evidence <https://www.w3.org/TR/vc-data-model/#evidence> property, which
> I read as ‘a means to facilitate data validation’ (while the validation
> itself is outside scope of the VC spec
> <https://www.w3.org/TR/vc-data-model/#dfn-credential-validation>).
>
>
>
> I see data validation
> <https://essif-lab.github.io/framework/docs/terms/validate> as an action
> that a party performs after it has received (and verified) data (e.g. a
> presentation). It results in a decision that says whether or not that data
> must be considered ‘valid’ for further processing, e.g. whether the party
> trusts the data sufficiently to continue to work with it, or in still other
> words: whether or not the risk of such processing being ‘invalid’ as a
> result of working with that data, is acceptable.
>
>
>
> One may readily observe that criteria that a party will use will depend on
> the context, the purpose for which the data will be used, the party’s risk
> appetite, etc. Validation criteria are highly context sensitive and
> subjective. There is no one-size-fits all.
>
>
>
> However, the (define time) specification of validation criteria, and the
> (run time) use thereof, will benefit from the presence of ‘assurances’,
> that may constitute of evidence that the data is produced or vetted in a
> specific way (by an official exam, a specific medical test), or by an actor
> that has specific qualifications (e.g. certificates, accreditations), etc.
>
>
>
> I see the ‘evidence’ property as the place to put data, that is evidence
> to whatever validators might be needing in (not so) specific cases, and
> that they could design validation criteria around.
>
>
>
> I think it is undecideable whether data should be ‘evidence’, or should be
> part of the credentialSubject object. That is because what one validator
> would consider assurance/evidence, another would consider as part of the
> data that it needs for further processing. Here’s an example
>
>
>
> Consider Alice, a patient that needs to transfer to an elderly home. Her
> application needs to come with her treatment plan, for which she has a
> credential, which has properties e.g., the organization on whose behalf the
> plan was drafted, and the qualifications of the person that drafted it. One
> elderly home may decide that the application is only valid if the treatment
> plan was drafted by a qualified nurse (“it’s the law”), in which case such
> qualifictions may be considered ‘evidence’. Another elderly home may decide
> that the application is valid if there is treatment plan, and use the
> qualifications of its author in the caring process, as input for
> determining when and how to review the treatment plan. In that case, the
> same data would not qualify as ‘evidence’ as intended by VC 1.1.
>
>
>
> Does this pose a problem? I think not. From the perspective of any
> validator (b.t.w., do we want to have this role in the SSI ecosystem?), it
> really doesn’t matter *where* the supporting data/evidence sits, as long
> as it can be found and the software they use can find and present it. With
> a properly defined schema that should be a big deal.
>
>
>
> Rieks
>
>
>
> *From:* Kerri Lemoie <klemoie@concentricsky.com>
> *Sent:* Thursday, April 7, 2022 11:04 AM
> *To:* W3C Credentials CG (Public List) <public-credentials@w3.org>
> *Cc:* public-vc-edu@w3.org
> *Subject:* VC Evidence Discussion
>
> Hello all,
>
> I’m seeking some input on VC evidence. This is a topic relevant for
> VC-EDU because education data specifications like Open Badges and CLR may
> contain an evidence property to support the achievement. This evidence
> could be a test score, a link to an image, video, and/or web page, etc.
> that demonstrates competency or participation. These specs are working
> towards aligning with VCs and it was originally thought that this type of
> evidence would be included as part of the credentialSubject if it existed.
>
> This would look something like this:
>
> https://json.link/21SpTf0rC4
>
> But since VCs already have an evidence property that allows for an array
> of evidence, it seems to make sense to use that property instead of using a
> separate property like the one demonstrated above. The rationalization is
> that VC evidence could be an array that supports what is needed for a
> credentialSubject to offer to support the verifiability of a VC such as a
> student id or it could also support the achievement that is being claimed
> as discussed above. This would look more like:
>
> https://json.link/0gqe5D1U4K
>
> Can you share your thoughts on this second approach? Do you think the
> VC.evidence support the achievement evidence too?
>
>
>
> Thanks!
>
>
>
> Kerri
>
>
>
>
>
>
> --------
>
> Kerri Lemoie, PhD
> Director, Digital Credentials Research & Innovation
>
> badgr.com <https://info.badgr.com/> | concentricsky.com
> she/her/hers
>
>
>
>
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>
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