Network Working Group C. Bormann
Internet-Draft Universität 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.
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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
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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