Re: [Cbor] Status of Appendix A in RFC 8949

[Anders Rundgren <[e-mail]>]

On 2023-05-05 11:17, Carsten Bormann wrote:
> On 2023-05-05, at 10:16, Anders Rundgren <[e-mail]> wrote:
>>
>> A diagnostic notation parser/decoder would generate 0x23 for -4.0.
> 
> When an application uses a dCBOR library to encode a -4.0, the CBOR generic data model will see a -4, which is shown as -4 in diagnostic notation and as 0x23 in the encoded data item.

For a "normal" developer (I think I am one), it is not very obvious how Appendix A can be normative if a compliant DN *parser* implementation may also encode -4.0 as 0x23, while the Appendix' 0xf90c400 is flagged as an invalid data item by decoders.

> 
> You can write an application that takes CBOR diagnostic notation for -4.0, ingests this to a CBOR generic data model, applies dCBOR rules to that, and then encodes it using CBOR deterministic encoding rules.  The diagnostic notation for the latter will show -4, not -4.0.

For the use-cases I'm thinking of, data models are a part of applications.  Application developers should be able to focus on how data models can be expressed in terms of available core data types (*), where CBOR gives you a pretty decent selection. Serialization issues should be invisible to the extent possible.

Anders

*) like they have to for SQL databases.
> 
> Grüße, Carsten
>