Network Working Group Y. Shafranovich
Internet-Draft SolidMatrix Technologies, Inc.
Expires: August 6, 2005 February 2, 2005
MIME Type for CSV Files
draft-shafranovich-mime-csv-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines MIME types "text/csv" and
"text/comma-separated-values" which used for Comma-Separated Values
(CSV) files.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. MIME Type Registration of text/csv and
text/comma-separated-values . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1 Normative References . . . . . . . . . . . . . . . . . . . 5
5.2 Informative References . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5
A. Appendix A - Discussion of the CSV format . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 8
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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 file is very common it has never
been formally documented. Additionally, while the IANA MIME
registration tree includes a registraton 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 formally register two MIME types for CSV in accordance with
RFC 2048 [4].
2. MIME Type Registration of text/csv and text/comma-separated-values
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 types text/csv and
text/comma-separated-values
MIME media type name: text
MIME subtype name: csv, comma-separated-values
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:
While section 4.1.1. of RFC 2046 [1] stipulates that "text"
subtypes MUST use a CRLF sequence as a line break, in practice
that is not always true for CSV. Therefore, implementors should
be aware that either CR or CRLF maybe used as a line break for
this format.
Security considerations:
CSV files contain passive text data which should not pose any
risks. However, it is possible in theory that malicious binary
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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 as described in
appendix A. The most common difference among various format is
whether double quotes (") are used to enclose strings.
Implementors should "be conservative in what you do, be liberal in
what you accept from others" (RFC 793 [2]) when processing CSV
files.
Published specification:
While numerous private specifications exist for various programs
and systems, there is no single "master" specification for this
format. A sampling of formats and discussion of differences is
included in appendix A.
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
3. IANA Considerations
After IESG approval, IANA is expected to register these two types
"text/csv" and "text/comma-separated-values" using the application
provided in this document.
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4. Security Considerations
See discussion above
5. References
5.1 Normative References
[1] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, November
1996.
[2] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981.
[3] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
5.2 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
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While there are various specifications and implementations for the
CSV format (for ex. [5], [6], [7] and [8]), no formal specification
exists. This causes a wide variety of interpretations for CSV files.
While this document does not seek to document the CSV format,
nevertheless we want 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 (either CR or CR/LF). 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:
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 (CR or CR/LF) and commas should be
enclosed in double-quotes. For example:
"aaa","b CRLF
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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"
8. Whitespace immediately before and after commas maybe removed
unless it appears inside double-quotes. For example:
zzz, yyy , xxx
would be processed as if it was:
zzz,yyy,xxx
The ABNF grammar [3] appears as follows:
COMMA = %x2C
file = [header] *record
end-of-field = COMMA / (CR / CRLF)
header = *(*WSP field *WSP end-of-field)
record = *(*WSP field *WSP end-of-field)
field = escaped / non-escaped
escaped = DQUOTE *(VCHAR / CR / CRLF / 3*DQUOTE) DQUOTE
non-escaped = *VCHAR
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Acknowledgment
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Internet Society.
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