Re: [Txauth] Polymorphism (Was: JSON Schema?)

Dick Hardt <dick.hardt@gmail.com> Mon, 06 July 2020 20:41 UTC

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From: Dick Hardt <dick.hardt@gmail.com>
Date: Mon, 6 Jul 2020 13:41:14 -0700
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To: Justin Richer <jricher@mit.edu>
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Subject: Re: [Txauth] Polymorphism (Was: JSON Schema?)
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Responding to Justin's polymorphism comments ...

On Mon, Jul 6, 2020 at 12:54 PM Justin Richer <jricher@mit.edu> wrote:

> Polymorphism in the protocol is an important part of the XYZ proposal’s
> design, and as a feature it directly addresses a number of the items you
> found when doing your XAuth implementation, like parsing OAuth scopes and
> dealing with the authorization/authorizations mutually-exclusive oddness
> that you mentioned. I strongly believe that GNAP should make use of a
> polymorphic protocol structure for these and other reasons. Polymorphism is
> a built-in feature of the JSON data model, and it’s also fully possible to
> support under CBOR and other data serialization languages. Even JWT most
> famously uses polymorphism for the “aud” field, which can be a string or an
> array of strings depending on context, all with clear semantics.
>

 I strongly disagree with "GNAP should make use of a polymorphic protocol
structure"

We should use it only if we really need it, and it makes implementations
simpler. I personally don't think it accomplished that in JWT with the
audience. I would bet there is a fair amount of code that does not check if
the 'aud' property is an array, it just assumes it is a string.

wrt. my authorization / authorizations oddness, polymorphism would not
solve it as the contents of both authorization / authorizations in XAuth
are objects.

/Dick