[Cbor] Re: EDN redux

[Carsten Bormann <[e-mail]>]

On 2024-08-07, at 17:41, Rohan Mahy <[e-mail]> wrote:
> 
> Hi Carsten, since you think so many people misunderstand what this document is for, maybe you could write your requirements so you're on the record. They certainly seem to have shifted at various points in this argument. 

The document sure did evolve: It started out as a brief description of the extension point.  Additional desirables were added over time, in particular the desirable for an ABNF definition of EDN, which in turn made it much easier to add support for somewhat relaxed, easier to use grammar (e.g., optional commas and an optional terminating comma that no longer fights with git).

> I think the most important value of EDN is to provide a well-specified, easy-to-use, JSON-like, human-readable and human-writable format that end-users can use to express CBOR instance documents, and can be converted in both directions. 

Yes.  
We wouldn’t need a new document for that, as RFC 8949 in conjunction with RFC 8610 already provides that.  
But we can still make it easier to use.  
E.g., time values can always be expressed as seconds since UNIX epoch, and had to be in 8949/8610 EDN.  
The current document adds an extension point that can be used for writing more readable expressions of CBOR data items, specifically via the dt’’ application-extension literal.

> Extending app-strings is pretty low on my list compared to any of the above, and certainly makes any machine-consumable conversion to/from CBOR instance docs more complicated.

Maybe this document is not really relevant for you then?

> To be clear, CBOR didn't define tag 999. This is yet another extra "feature" you've added to the EDN draft.

Tag 999 was defined out of experience of protocol evolution.
Enabling components of a system to tolerate the use of an extension point that they themselves do not support yet is desirable to sustain protocol evolution.  
Of course, this could be left out, making the deployability of the extension point much worse.  
You don’t care about the extension point, so that may seem trivial to you.

Grüße, Carsten