Network Working Group                                         C. Bormann
Internet-Draft                                    Universit├Ąt Bremen TZI
Intended status: Standards Track                        24 February 2022
Expires: 28 August 2022


                          Using CDDL for CSVs
                     draft-bormann-cbor-cddl-csv-00

Abstract

   The Concise Data Definition Language (CDDL), standardized in RFC
   8610, is defined to provide data models for data shaped like JSON or
   CBOR.

   Another representation format that is quote popular is the CSV file
   as defined by RFC 4180.

   The present document shows how to use CDDL to provide a data model
   for CSV files.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 28 August 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components



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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  CSV generic data model  . . . . . . . . . . . . . . . . . . .   2
   3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Concise Data Definition Language (CDDL), standardized in
   [RFC4180], is defined to provide data models for data shaped like
   JSON or CBOR.

   Another representation format that is quote popular is the CSV file
   as defined by [RFC4180].

   The present document shows how to use CDDL to provide a data model
   for CSV files.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This specification uses terminology from [RFC8610].

2.  CSV generic data model

   The CSV format is defined in [RFC4180].  The generic data model for
   the data in a CSV file can be described in CDDL as:







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   csv = [?header, *record]
   header = [+header-field]
   record = [+field]
   header-field = text
   field = text

   Note that the elements of this data model describe the interpretation
   of the data after removal of lexical structure such as newlines,
   commas, escape characters, and quotation marks.

   For the purposes of a specific application, the data model level
   structure of each field may be described in a more elaborate way,
   e.g., as a number.  CDDL currently does not have a way to express the
   transformation from the text string in the CSV field to the number
   that this text string represents at the application data model level;
   the usage of anything but "text" for a field therefore MUST be
   accompanied by an instruction how to perform the translation.  As a
   preferred choice, the JSON representation of the data model item, if
   it exists, MAY be chosen by that instruction.

   Since the CSV media type text/csv defaults to us-ascii (see Section 3
   of [RFC4180]), many uses of CSV will need to specify the media type
   parameter charset.  The media type parameter header MAY be used to
   indicate the presence or absence of a header line; if it is not
   given, the grammar MUST NOT be ambiguous about the presence of a
   header (i.e., it MUST be either mandatory or absent).

   Note that the ABNF [STD68] in [RFC4180] does not quite handle the
   case that charset is not us-ascii.  For the purposes of the present
   specification, the ABNF is understood to allow all characters from
   the charset except %x22 and %x2C in TEXTDATA.  For the purposes of
   the present specification, the ABNF rule CRLF is read as:

   CRLF = [CR] LF

   as is hinted in Section 3 of [RFC4180].

3.  Examples

   A simplified CSV form definition of a SID file [I-D.ietf-core-sid]
   might look like this:










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   ; header = absent

   SID-File = [meta-record,
               *dependency-record,
               *range-record,
               *item-record]

   meta-record = ["meta",
                  module-name: text,
                  module-revision: empty / text,
                  sid-file-revision: empty / text,
                  description: empty / text]

   dependency-record = ["dep",
                        module-name: text,
                        module-revision: text]

   range-record = ["range",
                   entry-point: uint,
                   size: uint]

   item-record = ["item",
                  namespace: "module" / "identity" / "feature" / "data",
                  identifier: yang-identifier / schema-node-path
                  ; the above probably should say which namespace
                  ; goes with which identifier
                  sid: uint]

   yang-identifier = text .abnf ("yang-identifier" .det id-abnf)
   schema-node-path = text .abnf ("schema-node-path" .det id-abnf)
   id-abnf = '
     schema-node-path = QID *( "/" OQID)
     yang-identifier = ID
     QID = ID ":" ID
     OQID = ID [":" ID]
     ID = I *C
     I = "_" / %x41-5a / %x61-7a
     C = I / %x30-39 / "-" / "."
   '

   empty = ""

   TODO: show the example in Appendix A of [I-D.ietf-core-sid]

4.  IANA Considerations

   This document makes no requests of IANA.




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5.  Security considerations

   The security considerations of [RFC8610] and [RFC4180] apply.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4180]  Shafranovich, Y., "Common Format and MIME Type for Comma-
              Separated Values (CSV) Files", RFC 4180,
              DOI 10.17487/RFC4180, October 2005,
              <https://www.rfc-editor.org/info/rfc4180>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/info/rfc8610>.

   [STD68]    Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

6.2.  Informative References

   [I-D.ietf-core-sid]
              Veillette, M., Pelov, A., Petrov, I., Bormann, C., and M.
              Richardson, "YANG Schema Item iDentifier (YANG SID)", Work
              in Progress, Internet-Draft, draft-ietf-core-sid-18, 18
              November 2021, <https://www.ietf.org/archive/id/draft-
              ietf-core-sid-18.txt>.

Acknowledgements

   Rob Wilton, unknowingly, made me write this specification.  I hope it
   will be useful.





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Author's Address

   Carsten Bormann
   Universit├Ąt Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany
   Phone: +49-421-218-63921
   Email: cabo@tzi.org










































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