Re: [Cbor] 🔔 Confirmation call for Working Group Adoption for draft-greevenbosch-appsawg-cbor-cddl

On 10/07/2017 08:11, Michael Richardson wrote:
> 
> Jeffrey Yasskin <jyasskin@chromium.org> wrote:
>     > The Chicago minutes [1] talk about people using CDDL to write
>     > specifications, but the -11 document is on the informational track
>     > rather than the standards track, meaning, I believe, that it's not
>     > intended to be referenced normatively from specifications. If folks do
>     > want to be able to use CDDL from standards, would the draft need to
>     > change tracks before it becomes a working group item?
> 
> I didn't think that CDDL would always require a normative reference from a
> standards track document.
> 
> My feeling is that if the structures are relatively simple that the CDDL is
> self-describing.  Most readers and implementers won't need to go further.

Unfortunately I don't think that's correct. It isn't just ABNF; there are
implied semantics in the constructs. For draft-ietf-anima-grasp, this is
the draft appendix I came up with to define the subset we use:

1. CDDL is expressed in ASCII characters.
2. Data items have identifiers. An identifier is a contiguous sequence of case-sensitive letters,
   digits, underscores ("_") and hyphens ("-") starting with a letter.
3. A comment is any text starting with a semi-colon (";") until the end of the line
4. Decimal integers have their normal meaning.
5. Text strings are enclosed by double quotation '"' characters.
6. The operator "=" means that the data item on its left is defined by the expression on its right.
7. The operator "/=" means that the data item on its left MAY be defined by the expression on its right.
In an expression:
8. Parentheses ("(", ")") delimit a syntactic unit.
9. Brackets ("[", "]") delimit a CBOR array.
10. In a CBOR array, items are separated by commas (",").
11. The prefix operator "+" indicates an item that occurs at least once.
12. The prefix operator "?" indicates an item that occurs zero or more times.
13. The infix operator "/" indicates a choice.
14. The infix operator ".." indicates an inclusive range.
15. The datatype name "bytes" indicates a byte string item
16. The datatype name "text" indicates a UTF-8 character string item.
17. The datatype name "uint" indicates an unsigned integer.
18. The datatype name "any" indicates any valid CBOR item.
19. The annotation ".size" precedes the size of a data item.
20. The annotation ".bits" precedes the bit number selected in a data item.
21. The annotation ".within" indicates that the data item on its left is subsetted from the item on its right.
22. "null" means a null value.

    Brian

> 
> I guess the question is what happens when more advanced constructs are
> needed.  In that case, I guess a normative reference would be required,
> and then the question would indeed arise.
> 
> 
> --
> Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
>  -= IPv6 IoT consulting =-
> 
> 
> 
> 
> 
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