Re: [Cbor] Co-occurrence constraints (Re: CDDL optionality and choices and optionality in CBOR and CDDL)

[Rohan Mahy <[e-mail]>]

Thanks, I'll try that in my data model in the morning.
-r

On Fri, Apr 12, 2024, 23:10 Carsten Bormann <[e-mail]> wrote:

> On 13. Apr 2024, at 02:49, Rohan Mahy <[e-mail]> wrote:
> >
> > Order = [
> >   food = [ * food_items ],
> >   ( includes_alcohol: true, drinks = [ * drink_items ] ) / (
> includes_alcohol: false, to_go: bool )
> > ]
>
> Almost (modulo some syntax issues).
> The constructs in the parentheses are CDDL groups, so you would need a
> group choice:
>
> > Order = [
> >   food: [ * food_item ],
> >   ( includes_alcohol: true, drinks: [ * drink_item ] //
> >     includes_alcohol: false, to_go: bool )
> > ]
>
> (Note the low operator precedence of group choices.
> I also used the singular form for the items, because each item is just one
> item.)
>
> This approach can solve a certain subset of the use cases that we call
> “co-occurrence constraints”; a more general solution usually requires some
> predicate language that in turn requires a navigation mechanism such as
> JSONPath [2].
>
> BTW:
>
> > bool = true / false
>
> You don’t have to say this, because it already is defined [almost] that
> way in the CDDL prelude [1].
> (Because of the “almost”, you actually cannot say it this way.)
>
> Grüße, Carsten
>
> [1]: https://www.rfc-editor.org/rfc/rfc8610.html#appendix-D
> [2]: https://www.rfc-editor.org/rfc/rfc9535.html
>
>