Network Working Group Y. Shafranovich
Internet-Draft SolidMatrix Technologies, Inc.
Expires: August 20, 2005 February 16, 2005
Common Format and MIME Type for CSV Files
draft-shafranovich-mime-csv-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document documents the format used for Comma-Separated Values
(CSV) files and registers the associated MIME type "text/csv".
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of the CSV format . . . . . . . . . . . . . . . . . 3
3. MIME Type Registration of text/csv . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1 Normative References . . . . . . . . . . . . . . . . . . . 6
7.2 Informative References . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
A. Status of This Document [To Be Removed Upon Publication] . . . 7
A.1 Discussion Venue . . . . . . . . . . . . . . . . . . . . . 7
A.2 Document Repository . . . . . . . . . . . . . . . . . . . 7
A.3 Document History . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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1. Introduction
The comma separated values format (CSV) has been used for exchanging
and converting data between various spreadsheet programs for quite
some time. Surprisingly, while this format is very common it has
never been formally documented. Additionally, while the IANA MIME
registration tree includes a registration for
"text/tab-separated-values" type, no MIME types have ever been
registered with IANA for CSV. At the same time, various programs and
operating systems have begun to use different MIME types for this
format, many of which vary from system to system. This document
seeks to document the format of comma separated values (CSV) files
and to formally register the "text/csv" MIME type for CSV in
accordance with RFC 2048 [4].
2. Definition of the CSV format
While there are various specifications and implementations for the
CSV format (for ex. [5], [6], [7] and [8]), no formal specification
exists which causes a wide variety of interpretations for CSV files.
This section seeks to document the format that seems to be followed
by most implementations:
1. Each record is located on a separate line delimited by a line
break (CRLF). For example:
aaa,bbb,ccc CRLF
zzz,yyy,xxx CRLF
2. The last record in the file may or may not have an ending
linebreak. For example:
aaa,bbb,ccc CRLF
zzz,yyy,xxx
3. There maybe an optional header line appearing as the first line
of the file with the same format as normal record lines. This
header will contain names corresponding to the fields in the file
and will usually contain the same number of fields as the records
in the rest of the file. For example:
field_name,field_name,field_name CRLF
aaa,bbb,ccc CRLF
zzz,yyy,xxx CRLF
4. Within the header and each record there may be one or more
fields, delimited by commas. The last field in the record may or
may not be followed by a comma. For example:
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aaa,bbb,ccc
5. Each field may or may not be enclosed in double quotes (however
some programs such as Microsoft Excel do not use double quotes at
all). For example:
"aaa","bbb","ccc" CRLF
zzz,yyy,xxx
6. Field containing line breaks (CRLF) and commas should be enclosed
in double-quotes. For example:
"aaa","b CRLF
bb","ccc" CRLF
zzz,yyy,xxx
7. If double-quotes are used to enclosed fields, then double-quotes
inside fields must be surounded by double quotes. For example:
"aaa","b"""bb","ccc"
The ABNF grammar [1] appears as follows:
file = [header CRLF] record *(CRLF record) [CRLF]
header = name *(COMMA name)
record = field *(COMMA field)
name = field
field = (escaped / non-escaped)
escaped = DQUOTE *(VCHAR / CR / LF / CRLF / 3*DQUOTE) DQUOTE
non-escaped = *VCHAR
COMMA = %x2C
CR = %x0D ;as per section 6.1 of RFC 2234 [1]
LF = %x0A ;as per section 6.1 of RFC 2234 [1]
CRLF = CR LF ;as per section 6.1 of RFC 2234 [1]
VCAR = %x21-7E ;as per section 6.1 of RFC 2234 [1]
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3. MIME Type Registration of text/csv
This section provides the media-type registration application (as per
RFC 2048 [4], which will be submitted to IANA after IESG approval of
this document.
To: ietf-types@iana.org
Subject: Registration of MIME media type text/csv
MIME media type name: text
MIME subtype name: csv
Required parameters: none
Optional parameters: charset
Common usage of CSV is US-ASCII, but other character sets as
defined by IANA for the "text" tree may be used.
Encoding considerations:
As per section 4.1.1. of RFC 2046 [2], this media type uses CRLF
to denote line breaks. However, implementors should be aware that
some implementations may use other values.
Security considerations:
CSV files contain passive text data which should not pose any
risks. However, it is possible in theory that malicious binary
data maybe included in order to exploit potential buffer overruns
in the program processing CSV data. Additionally, private data
maybe shared via this format (which of course applies to any text
data).
Interoperability considerations:
Due to lack of a single specification there are considerable
differences among different implementations. Implementors should
"be conservative in what you do, be liberal in what you accept
from others" (RFC 793 [3]) when processing CSV files. An attempt
at a common definition can be found in Section 2.
Published specification:
While numerous private specifications exist for various programs
and systems, there is no single "master" specification for this
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format. An attempt at documentating a common definition can be
found in Section 2.
Applications which use this media type:
Spreadsheet programs and various data conversion utilities
Additional information:
Magic number(s): none
File extension(s): CSV
Macintosh File Type Code(s): TEXT
Person & email address to contact for further information:
Yakov Shafranovich <ietf@shaftek.org>
Intended usage: COMMON
Author/Change controller: IESG
4. IANA Considerations
After IESG approval, IANA is expected to register the MIME type
"text/csv" using the application provided in Section 3 of this
document.
5. Security Considerations
See discussion above
6. Acknowledgments
The author would like to thank Dave Crocker, Martin Duerst and Bruce
Lilly for their helpful suggestions. A special word of thanks to
Dave for helping with the ABNF grammar.
7. References
7.1 Normative References
[1] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[2] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, November
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1996.
[3] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981.
7.2 Informative References
[4] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures",
BCP 13, RFC 2048, November 1996.
[5] Repici, J., "HOW-TO: The Comma Separated Value (CSV) File
Format", 2004,
<http://www.creativyst.com/Doc/Articles/CSV/CSV01.htm>.
[6] Edoceo, Inc., "CSV Standard File Format", 2004,
<http://www.edoceo.com/utilis/csv-file-format.php>.
[7] Rodger, R. and O. Shanaghy, "Documentation for Ricebridge CSV
Manager", February 2005,
<http://www.ricebridge.com/products/csvman/reference.htm>.
[8] Raymond, E., "The Art of Unix Programming, Chapter 5", September
2003,
<http://www.catb.org/~esr/writings/taoup/html/ch05s02.html>.
Author's Address
Yakov Shafranovich
SolidMatrix Technologies, Inc.
Email: ietf@shaftek.org
URI: http://www.shaftek.org
Appendix A. Status of This Document [To Be Removed Upon Publication]
A.1 Discussion Venue
Discussion about this document should be directed to the IETF-TYPES
mailing list <http://www.alvestrand.no/mailman/listinfo/ietf-types/>
which is also reachable via <ietf-types@iana.org>. Of course,
comments directly to the author are always welcome.
A.2 Document Repository
Copies of this and earlier versions including multiple formats can be
found at <http://www.shaftek.org/publications/drafts/mime-csv/>.
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A.3 Document History
Changes from draft-shafranovich-mime-csv-00 to
draft-shafranovich-mime-csv-01:
o Type "text/comma-separated-values" has been removed
o The "encoding consideration" paragraph of Section 3 has been
changed to allow CRLF only as per section 4.1.1. of RFC 2046 [2].
This has been reflected in the ABNF grammar in Section 2.
o ABNF grammar in Section 2 has been cleaned up.
o Acknowledgements and status sections were added.
o CSV format definition was moved to the normative section of the
document
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