[Cbor] Minutes IETF98 CBOR

[Francesca Palombini <[e-mail]>]

Hi all,

Here below you can read the minutes for the first CBOR meeting, big thanks to Paul and Henk for taking them!
Please let us know if you have any comment.

Francesca


CBOR WG Meeting
IETF 98 - Chicago
Thursday, March 30, 2017, 13:00 - 15:00
Chairs: Joe Hildebrand, Francesca Palombini Minutes taken by Paul Hoffman
                Text on the slides is not reproduced here
                See https://datatracker.ietf.org/meeting/98/session/cbor for slides
                Action items collected by Henk Birkholz


* Introduction  [15'] : Chairs
                First meeting of CBOR WG
                Using GitHub in general, not strictly
                Issues are discussed on the list


* CBOR specification status: Carsten Bormann
                https://tools.ietf.org/html/rfc7049
                Made defining new tags easy
                                May want to revisit the IANA considerations
                Kerry Lynn: is there test suite or test vectors?
                                Carsten: We have examples in the RFC
                                                Maybe this is a good time to start this
                                Joe: Has a pretty comprehensive suite in Node
                                                Also has a fuzzing suite
                                                Maybe pull that out as a separate repo
                Brian Carpenter: When a new tag is defined, does it go into the RFC?
                                Joe: There is an IANA registry
                                Carsten: Different levels of requirement
                                Joe: Do people have opinions about this policy? Say so on the list.
                                                Carsten: We may want to make this a bit harder because we are running out the 2-byte range
                                                Joe: We might give tag guidance
                                                Rick Taylor: DTN WG is using CBOR
                                                                Could use implementation guidance
                                Henk Birkholz: Where will these go?
                                                Carsten: Use a GitHub wiki
                                Ira McDonald: Opposed to the first-come, first-serve range
                                                Wants a minimum of specification required
                                                Dave Thayler: We need more reasons for this discussion
                                                Alexey Melnikov: We don't have to do this now
                                                Sean Leonard: We might want to get a specification for things that are generally used
                                                DaveT: Can't be guaranteed that you won't have a breaking change
                                Carsten: Shows the IANA repository
                                                The expert can give pushback on "specification required" before giving
                                                DaveT: Question in the industry about which of these can be converted to JSON
                                                                WG should be aware of conversions from JSON
                                                                Carsten: Document more that tags are voluntary
                                                James Woodyatt: When you have precious values, demand becomes high
                                                                6lo has some issues with this
                                                                May need a parsing switch into smaller tags
                                                                Michael Richardson: Asks the nature of the pressure
                                                                Carsten: it is reasonable that a tag could redefine the tag space inside
                                                                Sean: The tag is supposed to be globally understandable
                                                                                If you want to make something contextual, you can
                                                                                Joe: Can imagine a tag that switches context
                Action items:
                                * Joe will create repo for CBOR test & fuzzer suite in github cbor organization
                                * Carsten will place pointer to Joe's suites on cbor.io
                                * Carsten will start a wiki page for implementation guidelines
                                * Carsten will make more clear in text that you do not have to use tags
                                * Carsten will create specific text about outer and inner tags


* CDDL: Carsten
                https://datatracker.ietf.org/doc/draft-greevenbosch-appsawg-cbor-cddl/
                FDT = Formal Description Technique
                No semantics in CDDL today, only structure
                Many specs are using CDDL to encode JSON
                Let's not turn it into a scheme language, but keep it as structural
                Henk: We should come up with a consistent example that goes throughout the document
                DaveT: ABNF supports string concatenation
                                There are plenty of protocols don't need offsets
                Matt Miller: We should do things that present the least surprise
                                Computed values might give surprise
                Sean: Reuse syntax from other DLs
                                Maybe have a different syntax for regexps
                Dave Waltermire: Reduce computational complexity depending on where it will be used
                DaveT: No less expressive than JSON Schema?
                Hannes Tschofenig: Tried to push JSON Schema here but it might have been too complicated
                Matt: Rejection was a reaction to XML Schema, maybe an over-reaction
                Joe: What we are not doing here is a validation language; we are only do a specification language
                                Hannes: But COSE did code generation
                                Joe: Difference is in defaults for objects
                                                Try to stay away from validation because it has been wrong
                DaveT: If we want CDDL to be usable, we have to see what people are doing instead
                                Should not do what they are not needing
                Matt: We are trying to say what you can define JSON formally
                Henk: I can read this (RFC 7071 slide)
                                Validation is not our goal, it is a valuable side-effect
                Hannes: There was an assumption that implementers would use the schema, but they really wanted examples
                Michael: Unless the CDDL is defining bytes on the wire, we don't have to obsolete any of them
                Sean: Wants constraints
                                Numeric constraints should use a programming language construct
                DaveW: Non-text labels: doesn't that require some things here?
                Henk: The jump to validation is pretty tiny
                                Joe: We agree on structure, but need to get new consensus on validation
                Joe: Does anyone object to us starting with this document? (No objections in the room)
                                Lots have read this, surprising number have used it to write spec
                                Need to come up with a new name on the list before we come up with a WG draft
                                Spec to refer to quickly (current form) (small editorial pass), then start a -bis soon, versus work more on the spec
                                Rick: Quickly, and rip out verification for now
                                Jim Schaad: Quickly, easy for people to read
                                                Do the authors think that any feature is underspecified?
                                                Henk: within-template needs a bit more focus, but it is used well
                                Brian: Quickly
                                James: Has written an internal spec, doesn't need it rushed
                                                Found a few places (esp the generic syntax) the could use a bit more focus
                                DaveW: What will be cut?
                                Henk: Notify every author who is using it
                                Hannes: Feels like there is a rush but there was not before
                                Rick: We should have an audit of documents in the pipeline
                                Matt: Start with things in the RFC Editor queue
                Action items:
                                * Henk will make the convention of expressing constants in UPPER CASE explicit
                                * Henk will create text to illustrate purpose: interaction between humans and machines
                                * Generic Types: Carsten will take a shot at that being a little bit underspecified
                                * Henk will prepare a branch for an expediated draft polish
                                * Carsten will lead the discussion if we need a new name for cddl
                                * Carsten will review IANA considerations for "specification required"
so there is a field to record IETF change control


* Array tags: Carsten
                https://datatracker.ietf.org/doc/draft-jroatch-cbor-tags/
                Joe: Reserving this many tags in one-byte space is overkill
                Rick: How do you represent flags here

* Time tags: Carsten
                https://tools.ietf.org/html/draft-bormann-cbor-time-tag-00
                The tags in CBOR only solve 85% of the hard time problem
                Also talked about draft-bormann-lpwan-cbor-template

* OID: Sean
                https://datatracker.ietf.org/doc/draft-bormann-cbor-tags-oid/
                Carsten: How do we decide to change registrations to give them shorter tags?
                                Joe: Wants the docs to be short and easy to understand
                                                Contact authors to see if they want to do the work here
                                Maybe has a draft with a UUID
                Alexey: Do the earlier registrations have a change control field?
                                Joe: They should