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Versions: 00 01 02 03 04 05 RFC 4180

Network Working Group                                    Y. Shafranovich
Internet-Draft                            SolidMatrix Technologies, Inc.
Expires: October 7, 2005                                   April 5, 2005


               Common Format and MIME Type for CSV Files
                   draft-shafranovich-mime-csv-05.txt

Status of this Memo

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   This Internet-Draft will expire on October 7, 2005.

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  . . . . . . . . . . . . . . . . . . .  7
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     7.1   Normative References . . . . . . . . . . . . . . . . . . .  7
     7.2   Informative References . . . . . . . . . . . . . . . . . .  7
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  8
   A.  Status of This Document [To Be Removed Upon Publication] . . .  8
     A.1   Discussion Venue . . . . . . . . . . . . . . . . . . . . .  8
     A.2   Document Repository  . . . . . . . . . . . . . . . . . . .  8
     A.3   Document History . . . . . . . . . . . . . . . . . . . . .  8
       Intellectual Property and Copyright Statements . . . . . . . . 10


































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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
   [1].

2.  Definition of the CSV format

   While there are various specifications and implementations for the
   CSV format (for ex. [4], [5], [6] and [7]), 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 line
       break.  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 should contain the same number of fields as the records in
       the rest of the file (the presence or absence of the header line
       should be indicated via the optional "header" parameter of this
       MIME type).  For example:

       field_name,field_name,field_name CRLF
       aaa,bbb,ccc CRLF
       zzz,yyy,xxx CRLF





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   4.  Within the header and each record there may be one or more
       fields, separated by commas.  Each line should contain the same
       number of fields throughout the file.  The last field in the
       record 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).  If fields are not enclosed with double quotes, then double
       quotes may not appear inside the fields.  For example:

       "aaa","bbb","ccc" CRLF
       zzz,yyy,xxx

   6.  Field containing line breaks (CRLF), double quotes 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 a double-quote
       appearing inside a field must be escaped by preceding it with
       another double quote.  For example:

       "aaa","b""bb","ccc"

   The ABNF grammar [2] 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 *(TEXTDATA / COMMA / CR / LF / 2DQUOTE) DQUOTE

      non-escaped = *TEXTDATA

      COMMA = %x2C

      CR = %x0D ;as per section 6.1 of RFC 2234 [2]




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      DQUOTE =  %x22 ;as per section 6.1 of RFC 2234 [2]

      LF = %x0A ;as per section 6.1 of RFC 2234 [2]

      CRLF = CR LF ;as per section 6.1 of RFC 2234 [2]

      TEXTDATA =  %x20-21 / %x23-2B / %x2D-7E


3.  MIME Type Registration of text/csv

   This section provides the media-type registration application (as per
   RFC 2048 [1], 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, header

      Common usage of CSV is US-ASCII, but other character sets as
      defined by IANA for the "text" tree may be used in conjuction with
      the "charset" parameter.

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

   Encoding considerations:

      As per section 4.1.1. of RFC 2046 [3], 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



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      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 [8]) when processing CSV files.  An attempt
      at a common definition can be found in Section 2.

      Implementations deciding not to use the optional "header"
      parameter must make their own decision as to whether the header is
      absent or present.

   Published specification:

      While numerous private specifications exist for various programs
      and systems, there is no single "master" specification for this
      format.  An attempt at 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.




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5.  Security Considerations

   See discussion above

6.  Acknowledgments

   The author would like to thank Dave Crocker, Martin Duerst, Joel M.
   Halpern, Clyde Ingram, Graham Klyne, Bruce Lilly, Chris Lilley and
   members of the IESG for their helpful suggestions.  A special word of
   thanks to Dave for helping with the ABNF grammar.

   The author would also like to thank Henrik Lefkowetz, Marshall Rose
   and the folks at xml.resource.org for providing many of the tools
   used for preparing RFCs and Internet drafts.

7.  References

7.1  Normative References

   [1]  Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
        Mail Extensions (MIME) Part Four: Registration Procedures",
        BCP 13, RFC 2048, November 1996.

   [2]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [3]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046,
        November 1996.

7.2  Informative References

   [4]  Repici, J., "HOW-TO: The Comma Separated Value (CSV) File
        Format", 2004,
        <http://www.creativyst.com/Doc/Articles/CSV/CSV01.htm>.

   [5]  Edoceo, Inc., "CSV Standard File Format", 2004,
        <http://www.edoceo.com/utilis/csv-file-format.php>.

   [6]  Rodger, R. and O. Shanaghy, "Documentation for Ricebridge CSV
        Manager", February 2005,
        <http://www.ricebridge.com/products/csvman/reference.htm>.

   [7]  Raymond, E., "The Art of Unix Programming, Chapter 5",
        September 2003,
        <http://www.catb.org/~esr/writings/taoup/html/ch05s02.html>.

   [8]  Postel, J., "Transmission Control Protocol", STD 7, RFC 793,



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        September 1981.


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/>.

A.3  Document History

   Changes from draft-shafranovich-mime-csv-04 to
   draft-shafranovich-mime-csv-05:

   o  Fixes in ABNF grammar: comma excluded from TEXTDATA and added to
      escaped text, 2*DQUOTE changed to 2DQUOTE.

   Changes from draft-shafranovich-mime-csv-03 to
   draft-shafranovich-mime-csv-04:

   o  Fixed ABNF grammar in response to IESG comments: VCHAR changed to
      TEXTDATA, DQUOTE excluded from TEXTDATA, spaces are included in
      TEXTDATA, CRLF taken out since CR and LF are already included.

   o  Added clarification that double quotes may not be included inside
      non-quoted fields.

   o  Added clarification that the same number of fields should appear
      in every line.

   o  Added the optional "header" parameter to indicate the presence or
      absence of a header line.



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   Changes from draft-shafranovich-mime-csv-02 to
   draft-shafranovich-mime-csv-03:

   o  Changed text to prohibit the last field ending with a comma
      matching the ABNF grammar

   o  The double quote escaping is now set to two double quotes instead
      of three

   o  Moved some of the references between informative and normative
      sections

   Changes from draft-shafranovich-mime-csv-01 to
   draft-shafranovich-mime-csv-02:

   o  Minor errors in ABNF grammar corrected in response to AD comments

   o  Minor spelling mistakes corrected

   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 [3].
      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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