Network Working Group                                         C. BormannInternet-Draft                                    Universität Bremen TZIIntended status: Standards Track                             H. BirkholzExpires: 4 March 2026                                     Fraunhofer SIT                                                          31 August 2025                          Using CDDL for CSVs                     draft-bormann-cbor-cddl-csv-07Abstract   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   (Comma-Separated Values) file as defined by RFC 4180.   The present document shows a way 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.   Internet-Drafts are working documents of the Internet Engineering   Task Force (IETF).  Note that other groups may also distribute   working documents as Internet-Drafts.  The list of current Internet-   Drafts is at https://datatracker.ietf.org/drafts/current/.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time.  It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."   This Internet-Draft will expire on 4 March 2026.Copyright Notice   Copyright (c) 2025 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   Provisions Relating to IETF Documents (https://trustee.ietf.org/   license-info) in effect on the date of publication of this document.   Please review these documents carefully, as they describe your rightsBormann & Birkholz        Expires 4 March 2026                  [Page 1]Internet-Draft                CDDL for CSVs                  August 2025   and restrictions with respect to this document.  Code Components   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  . . . . . . . . . . . . . . . . . . . . . . . . . .   4   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5   5.  Security considerations . . . . . . . . . . . . . . . . . . .   5   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6   Appendix A.  Example: ietf-system.sid represented in CSV  . . . .   7   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   9   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   91.  Introduction   The Concise Data Definition Language (CDDL), standardized in   [RFC8610], 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   [BCP14] (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:Bormann & Birkholz        Expires 4 March 2026                  [Page 2]Internet-Draft                CDDL for CSVs                  August 2025   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 processing and 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.  A recently published CDDL extension, [RFC9741],   provides some CDDL control operators that could be used to express   the transformation between the text string in the CSV field and the   number that this text string represents at the application data model   level; this could be explored in future revisions of this   specification.  For now, 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 using the US-ASCII   character set (i.e., [STD80]; see Section 3 of [RFC4180]), many uses   of CSV will need to specify the media type parameter charset.  (Note   that CDDL can describe text information that is in UTF-8 form, which   includes US-ASCII as that is a subset of UTF-8.  If a different form   that is not a subset of UTF-8 is really still needed, some rules for   conversion will need to be defined by the application.)   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].Bormann & Birkholz        Expires 4 March 2026                  [Page 3]Internet-Draft                CDDL for CSVs                  August 20253.  Examples   A simplified CSV form definition of a SID file [RFC9595] might look   like this:   ; header = absent   SID-File = [meta-record,               ?description-record,               *dependency-record,               *range-record,               *item-record]   meta-record = ["ietf-sid-file",                  module-name: text,                  module-revision: empty / text,                  sid-file-revision: empty / text,                  sid-file-status: empty / "unpublished" / "published"]   description-record = ["description",                         description: empty / text]   dependency-record = ["dependency",                        module-name: text,                        module-revision: text]   range-record = ["range",                   entry-point: uint,                   size: uint]   item-record = [; "item", -- useful to elide for bulk of file                  sid: uint                  (                    namespace: "module" / "identity" / "feature"                    identifier: yang-identifier                   //                    namespace: "data"                    identifier: schema-node-path                  )                  status: empty / "stable" / "unstable" / "obsolete"]   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]Bormann & Birkholz        Expires 4 March 2026                  [Page 4]Internet-Draft                CDDL for CSVs                  August 2025     ID = I *C     I = "_" / %x41-5a / %x61-7a     C = I / %x30-39 / "-" / "."   '   empty = ""   This CDDL data model assumes that the text strings representing the   numbers entry-point, size, and sid are converted to uint.  (Note   that, due to the way YANG-JSON [RFC7951] defines the representation   of uint64 data items, these actually are text strings in JSON, which   in CSV is indistinguishable from numbers.  However, the CDDL model   for the CSV files will be more useful if it takes into account   typical CSV applications that automatically convert integer-like text   strings into numbers.)   The result of representing in CSV the sid file ietf-system.sid (as   defined in Appendix A of [RFC9595]) is shown in Appendix A.4.  IANA Considerations   This document makes no requests of IANA.5.  Security considerations   The security considerations of [RFC8610] and [RFC4180] apply.6.  References6.1.  Normative References   [BCP14]    Best Current Practice 14,              <https://www.rfc-editor.org/info/bcp14>.              At the time of writing, this BCP comprises the following:              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>.              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>.   [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/rfc/rfc4180>.Bormann & Birkholz        Expires 4 March 2026                  [Page 5]Internet-Draft                CDDL for CSVs                  August 2025   [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/rfc/rfc8610>.   [STD68]    Internet Standard 68,              <https://www.rfc-editor.org/info/std68>.              At the time of writing, this STD comprises the following:              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   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",              RFC 7951, DOI 10.17487/RFC7951, August 2016,              <https://www.rfc-editor.org/rfc/rfc7951>.   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,              "Handling Long Lines in Content of Internet-Drafts and              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,              <https://www.rfc-editor.org/rfc/rfc8792>.   [RFC9595]  Veillette, M., Ed., Pelov, A., Ed., Petrov, I., Ed.,              Bormann, C., and M. Richardson, "YANG Schema Item              iDentifier (YANG SID)", RFC 9595, DOI 10.17487/RFC9595,              July 2024, <https://www.rfc-editor.org/rfc/rfc9595>.   [RFC9741]  Bormann, C., "Concise Data Definition Language (CDDL):              Additional Control Operators for the Conversion and              Processing of Text", RFC 9741, DOI 10.17487/RFC9741, March              2025, <https://www.rfc-editor.org/rfc/rfc9741>.   [STD80]    Internet Standard 80,              <https://www.rfc-editor.org/info/std80>.              At the time of writing, this STD comprises the following:              Cerf, V., "ASCII format for network interchange", STD 80,              RFC 20, DOI 10.17487/RFC0020, October 1969,              <https://www.rfc-editor.org/info/rfc20>.Bormann & Birkholz        Expires 4 March 2026                  [Page 6]Internet-Draft                CDDL for CSVs                  August 2025Appendix A.  Example: ietf-system.sid represented in CSV   This appendix shows the CSV file that is automatically generated from   Appendix A of [RFC9595].  (Note that plaintext-based RFCs are limited   to 72 columns; therefore five long lines in the CSV file have been   folded as defined in [RFC8792].)   =============== NOTE: '\' line wrapping per RFC 8792 ================   ietf-sid-file,ietf-system,2014-08-06,,   description,Example sid file   dependency,ietf-yang-types,2013-07-15   dependency,ietf-inet-types,2013-07-15   dependency,ietf-netconf-acm,2018-02-14   dependency,iana-crypt-hash,2014-08-06   range,1700,100   1700,module,ietf-system,   1701,identity,authentication-method,   1702,identity,local-users,   1703,identity,radius,   1704,identity,radius-authentication-type,   1705,identity,radius-chap,   1706,identity,radius-pap,   1707,feature,authentication,   1708,feature,dns-udp-tcp-port,   1709,feature,local-users,   1710,feature,ntp,   1711,feature,ntp-udp-port,   1712,feature,radius,   1713,feature,radius-authentication,   1714,feature,timezone-name,   1715,data,/ietf-system:set-current-datetime,   1775,data,/ietf-system:set-current-datetime/input,   1776,data,/ietf-system:set-current-datetime/input/current-datetime,   1717,data,/ietf-system:system,   1718,data,/ietf-system:system-restart,   1719,data,/ietf-system:system-shutdown,   1720,data,/ietf-system:system-state,   1721,data,/ietf-system:system-state/clock,   1722,data,/ietf-system:system-state/clock/boot-datetime,   1723,data,/ietf-system:system-state/clock/current-datetime,   1724,data,/ietf-system:system-state/platform,   1725,data,/ietf-system:system-state/platform/machine,   1726,data,/ietf-system:system-state/platform/os-name,   1727,data,/ietf-system:system-state/platform/os-release,   1728,data,/ietf-system:system-state/platform/os-version,   1729,data,/ietf-system:system/authentication,   1730,data,/ietf-system:system/authentication/user,Bormann & Birkholz        Expires 4 March 2026                  [Page 7]Internet-Draft                CDDL for CSVs                  August 2025   1731,data,/ietf-system:system/authentication/user-authentication-\                                                                  order,   1732,data,/ietf-system:system/authentication/user/authorized-key,   1733,data,/ietf-system:system/authentication/user/authorized-key/\                                                              algorithm,   1734,data,/ietf-system:system/authentication/user/authorized-key/key\                                                                  -data,   1735,data,/ietf-system:system/authentication/user/authorized-key/\                                                                   name,   1736,data,/ietf-system:system/authentication/user/name,   1737,data,/ietf-system:system/authentication/user/password,   1738,data,/ietf-system:system/clock,   1739,data,/ietf-system:system/clock/timezone-name,   1740,data,/ietf-system:system/clock/timezone-utc-offset,   1741,data,/ietf-system:system/contact,   1742,data,/ietf-system:system/dns-resolver,   1743,data,/ietf-system:system/dns-resolver/options,   1744,data,/ietf-system:system/dns-resolver/options/attempts,   1745,data,/ietf-system:system/dns-resolver/options/timeout,   1746,data,/ietf-system:system/dns-resolver/search,   1747,data,/ietf-system:system/dns-resolver/server,   1748,data,/ietf-system:system/dns-resolver/server/name,   1749,data,/ietf-system:system/dns-resolver/server/udp-and-tcp,   1750,data,/ietf-system:system/dns-resolver/server/udp-and-tcp/\                                                                address,   1751,data,/ietf-system:system/dns-resolver/server/udp-and-tcp/port,   1752,data,/ietf-system:system/hostname,   1753,data,/ietf-system:system/location,   1754,data,/ietf-system:system/ntp,   1755,data,/ietf-system:system/ntp/enabled,   1756,data,/ietf-system:system/ntp/server,   1757,data,/ietf-system:system/ntp/server/association-type,   1758,data,/ietf-system:system/ntp/server/iburst,   1759,data,/ietf-system:system/ntp/server/name,   1760,data,/ietf-system:system/ntp/server/prefer,   1761,data,/ietf-system:system/ntp/server/udp,   1762,data,/ietf-system:system/ntp/server/udp/address,   1763,data,/ietf-system:system/ntp/server/udp/port,   1764,data,/ietf-system:system/radius,   1765,data,/ietf-system:system/radius/options,   1766,data,/ietf-system:system/radius/options/attempts,   1767,data,/ietf-system:system/radius/options/timeout,   1768,data,/ietf-system:system/radius/server,   1769,data,/ietf-system:system/radius/server/authentication-type,   1770,data,/ietf-system:system/radius/server/name,   1771,data,/ietf-system:system/radius/server/udp,   1772,data,/ietf-system:system/radius/server/udp/address,   1773,data,/ietf-system:system/radius/server/udp/authentication-port,Bormann & Birkholz        Expires 4 March 2026                  [Page 8]Internet-Draft                CDDL for CSVs                  August 2025   1774,data,/ietf-system:system/radius/server/udp/shared-secret,Acknowledgements   Rob Wilton, unknowingly, made us write this specification.  We hope   it will be useful.  Laurent Toutain inspired the SID CDDL format with   an example.Authors' Addresses   Carsten Bormann   Universität Bremen TZI   Postfach 330440   D-28359 Bremen   Germany   Phone: +49-421-218-63921   Email: cabo@tzi.org   Henk Birkholz   Fraunhofer SIT   Rheinstrasse 75   64295 Darmstadt   Germany   Email: henk.birkholz@sit.fraunhofer.deBormann & Birkholz        Expires 4 March 2026                  [Page 9]