Unicode Separated Values (USV)

Internet-Draft	Unicode Separated Values (USV)	January 2024
Henderson	Expires 4 July 2024	[Page]

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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 rights 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.¶

1. Introduction

Unicode Separated Values (USV) is a data format useful for exchanging and converting data between various spreadsheet programs, databases, and streaming data services. This RFC explains USV.¶

Additionally, we propose a new media type "text/usv", to be registered with IANA.¶

We provide information references for a USV git repository [usv-git-repository] and a programming implementation as a USV Rust crate [usv-rust-crate].¶

1.1. Requirements Language

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.¶

3. Definition of the USV Format

3.1. Data

Data is comprised of units, records, groups, and files.¶

3.2. Unit

A unit is comprised of content characters. It runs until a unit separator.¶

Example unit and unit separator:¶

<CODE BEGINS> file "unit-and-unit-separator.usv"


aaa␟


<CODE ENDS>

3.3. Record

A record is comprised of units. It runs until a record separator.¶

Example record and record separator:¶

<CODE BEGINS> file "record-and-record-separator.usv"


aaa␟bbb␟␞


<CODE ENDS>

3.4. Group

A group is comprised of records. It runs until a group separator.¶

Example group and group separator:¶

<CODE BEGINS> file "group-and-group-separator.usv"


aaa␟bbb␟␞ccc␟ddd␟␞␝


<CODE ENDS>

3.5. File

A file is comprised of groups. It runs until a file separator.¶

Example file and file separator:¶

<CODE BEGINS> file "file-and-file-separator.usv"


aaa␟bbb␟␞ccc␟ddd␟␞␝eee␟fff␟␞ggg␟hhh␟␞␝␜


<CODE ENDS>

3.6. Header

There may be an optional header appearing as the first item and with the same format as normal items. This header will contain names corresponding to the fields in the data, and should contain the same number of fields as the rest of data. The presence or absence of the header line should be indicated via the optional "header" parameter of this media type.¶

For example:¶

<CODE BEGINS> file "header.usv"


name␟name␟␞aaa␟bbb␟␞


<CODE ENDS>

4. ABNF grammar

4.1. Semantics

usv = *files¶

file = *groups¶

group = *records¶

record = *units¶

unit = *content-characters¶

4.2. Syntax

usv = 0*1( header ) body 0*1( ETB ); anything after is chaff¶

header = 1( unit_run / record_run / group_run / file_run )¶

body = *( unit_run / record_run / group_run / file_run )¶

file_run = *( file FS ) file ; next MUST be ( FS / ETB )¶

group_run = *( group GS ) group ; next MUST be ( GS / FS / ETB )¶

record_run = *( record RS ) record ; next MUST be ( RS / GS / FS / ETB )¶

unit_run = *( unit US ) unit ; next MUST be ( US / RS / GS / FS / ETB )¶

4.3. Character classes

content-character = *( typical-character / ESC '*' )¶

typical-character = '*' - special-character¶

special-character = US / RS / GS / FS / ESC / ETB¶

escape-character = ESC ( special-character / typical-character )¶

4.4. Unicode symbols

US = U+241F Symbol for Unit Separator (US)¶

RS = U+241E Symbol for Record Separator (RS)¶

GS = U+241D Symbol for Group Separator (GS)¶

FS = U+241C Symbol for File Separator (FS)¶

ESC = U+241B Symbol for Escape (ESC)¶

ETB = U+2417 Symbol for End of Transmission Block (ETB)¶

5. Examples

5.1. Hello World

This kind of data …¶

<CODE BEGINS> file "hello-world.txt"


hello, world


<CODE ENDS>

… is represented in USV as two units:¶

<CODE BEGINS> file "hello-world.usv"


hello␟world␟


<CODE ENDS>

Optional: if you prefer to see one unit per line, then end each line with a USV escape:¶

<CODE BEGINS> file "hello-world-with-lines.usv"


hello␟␛
world␟␛


<CODE ENDS>

5.2. Hello World Goodnight Moon

This kind of data …¶

<CODE BEGINS> file "hello-world-goodnight-moon.txt"


[ hello, world ], [ goodnight, moon ]


<CODE ENDS>

… is represented in USV as two records, each with two units:¶

<CODE BEGINS> file "hello-world-goodnight-moon.usv"


hello␟world␞goodnight␟moon␞


<CODE ENDS>

Optional: if you prefer to see one record per line, then end each line with a USV escape:¶

<CODE BEGINS> file "hello-world-goodnight-moon-with-lines.usv"


hello␟world␞␛
goodnight␟moon␞␛


<CODE ENDS>

5.3. Units, Records, Groups, Files

USV with 2 units by 2 records by 2 groups by 2 files:¶

<CODE BEGINS> file "units-records-groups-files.usv"


a␟b␞c␟d␝e␟f␞g␟h␜i␟j␞k␟l␝m␟n␞o␟p␜


<CODE ENDS>

This is what the USV can look like when you display it with a simple display tool:¶

<CODE BEGINS> file "units-records-groups-files-with-lines.usv"


a,b
c,d
-
e,f
g,h
=
i,j
k,l
-
m,n
o,p


<CODE ENDS>

5.4. Articles

USV can format paragraphs, such as in this example data stream of articles:¶

<CODE BEGINS> file "articles.usv"


Title One
␟
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip.
␞
Title Two
␟
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident,
sunt in culpa qui officia deserunt mollit anim id est laborum.
␞
Title Three
␟
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium
doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore
veritatis et quasi architecto beatae vitae dicta sunt explicabo.
␞


<CODE ENDS>

6. Source Code Examples

Hello World using Rust and the USV crate¶

<CODE BEGINS> file "usv-rust-crate-units.rs"


use usv::*;
let input = "hello␟world␟";
let records = input.units().collect();


<CODE ENDS>

Hello World Goodnight Moon using Rust and the USV crate¶

<CODE BEGINS> file "usv-rust-crate-records.rs"


use usv::*;
let input = "hello␟world␞goodnight␟moon␞";
let records = input.records().collect();


<CODE ENDS>

7. MIME media type registration for text/usv

This section provides the MIME media type registration application information.¶

To: ietf-types@iana.org¶

Subject: Registration of MIME media type text/usv¶

MIME media type name: text¶

MIME subtype name: usv¶

Required parameters: none¶

7.1. Optional parameters: charset, header

Common usage of USV is UTF-8, but other character sets defined by IANA for the "text" tree may be used in conjunction with the "charset" parameter.¶

The "header" parameter indicates the presence or absence of the header line. Valid values are "present" or "absent". Implementors choosing not to use this parameter must make their own decisions as to whether the header line is present or absent.¶

7.2. Encoding considerations

This media type uses LF to denote line breaks. However, implementors should be aware that some implementations may not conform i.e. may incorrectly use other values.¶

7.3. Security considerations

USV files contain passive text data that should not pose any risks. However, it is possible in theory that malicious binary data may be included in order to exploit potential buffer overruns in the program processing USV data. Additionally, private data may be shared via this format (which of course applies to any text data).¶

Apple macOS File Type Code(s): TEXT¶

Intended usage: COMMON¶

Author/Change controller: IESG¶

Contact: Joel Parker Henderson <joel@joelparkerhenderson.com>¶

10. References

10.1. Normative References

[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>.
[RFC2234]: Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, DOI 10.17487/RFC2234, November 1997, <https://www.rfc-editor.org/info/rfc2234>.
[RFC2048]: Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", RFC 2048, DOI 10.17487/RFC2048, November 1996, <https://www.rfc-editor.org/info/rfc2048>.
[RFC2046]: Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, <https://www.rfc-editor.org/info/rfc2046>.

10.2. Informative References

[usv-git-repository]: Henderson, J., "USV repository at https://github.com/sixarm/usv", 2022.
[usv-rust-crate]: Henderson, J., "USV rust crate at https://crates.io/crates/usv", 2024.
[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>.