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Network Working Group                                   A. Phillips, Ed.
Internet-Draft                                               Yahoo! Inc.
Expires: February 25, 2008                               August 24, 2007


                         The record-jar Format
                      draft-phillips-record-jar-01

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Copyright Notice

   Copyright (C) The IETF Trust (2007).















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Abstract

   The record-jar format provides a method of storing multiple records
   with a variable repertoire of fields in a text format.  This document
   provides a description of the format.  Comments are solicited and
   should be addressed to the mailing list 'record-jar@yahoogroups.com'
   and/or the author.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Format and Grammar . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Folding of Field Values  . . . . . . . . . . . . . . . . .  5
     2.2.  Comments . . . . . . . . . . . . . . . . . . . . . . . . .  7
     2.3.  Characters, Encodings, and Escapes . . . . . . . . . . . .  7
   3.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     4.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 13




























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1.  Introduction

   The record-jar format was originally described by The Art of Unix
   Programming [AOUP].  This format is useful for storing information in
   a human-readable text form, while making the data available for
   machine processing.  It is a flexible format, since it provides for
   an arbitrary range of fields in any given record and can be used to
   store data with variable length and content.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].







































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2.  Format and Grammar

   The record-jar format is described by the following ABNF ([RFC4234]):

   record-jar   = [encodingSig] [separator] *record
   record       = 1*field separator
   field        = ( field-name field-sep field-body CRLF )
   field-name   = *character
   field-sep    = *SP ":" *SP
   field-body   = *(continuation 1*character)
   continuation = ["\"] [[*SP CRLF] 1*SP]
   separator    = [blank-line] *("%%" [comment] CRLF)
   comment      = SP *69(character)
   character    = SP / ASCCHAR / UNICHAR / ESCAPE
   encodingSig  = "%%encoding" field-sep
                    *(ALPHA / DIGIT / "-" / "_") CRLF
   blank-line   = WSP CRLF

   ; ASCII characters except %x26 (&) and %x5C (\)
   ASCCHAR      = %x21-25 / %x27-5B / %x5D-7E
   UNICHAR      = %x80-%x10FFFF                      ; Unicode chars
   ESCAPE       = "\" ("\" / "&" / "r" / "n" / "t" )
                / "&#x" 2*6HEXDIG ";"

                              record-jar ABNF

   The record-jar format consists of character data that forms a
   sequence of records.  Each record is separated from other records by
   at least one line beginning with the sequence "%%" (%x25.25).
   Records are made up of one or more fields and a record MAY contain as
   many or as few fields as are necessary to convey the necessary data.
   Empty records and blank lines are ignored.

   A field is a single, logical line of characters from the Universal
   Character Set (Unicode) [Unicode], comprised of three parts: the
   field-name, the field-separator, and the field body.

   The field-name is an identifer.  Field-names SHOULD consist only of
   characters permitted in identifiers according to Unicode Standards
   Annex #31 (UAX#31) [UAX31] and SHOULD start only with characters with
   the property ID_Start.  Often field-names are further restricted to a
   sequence of letters and digits from the US-ASCII character set
   [ISO646].  A field-name SHOULD be treated as case sensitive and MUST
   NOT contain any spaces.  Upper and lowercase letters are often used
   to visually break up the name, for example using CamelCase.  It is a
   common convention that field names use an initial capital letter,
   although this is not enforced.  The hyphen-minus character ("-",
   %x2D) MAY be used to separate parts of the name visually, however, it



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   MUST NOT appear at the beginning or end of a field-name.

   The field separator (field-sep) is the colon character (":", %x3A).
   The separator MAY be surrounded on either side by any amount of
   horizontal whitespace (tab or space characters).  The normal
   convention is one space on each side.

   The field-body contains the data value.  Logically, the field-body
   consists of a single line of text using any combination of characters
   from the Universal Character Set followed by a CRLF (newline).  The
   carriage return, newline, and tab characters, when they occur in the
   data value stored in the field-body, are represented by their common
   backslash escapes ("\r", "\n", and "\t" respectively).  See
   Section 2.3 for more information on escape sequences.

2.1.  Folding of Field Values

   Some protocols limit total line length.  For example, many Internet
   plain-text protocols limits lines to 72 total bytes.  To accommodate
   such limits or for readability and presentational purposes, the
   field-body portion of a field can be split into a multiple-line
   representation; this is called "folding".

   Successive lines in the same field-body begin with one or more
   whitespace characters.  When processing the record-jar format, the
   linear whitespace (including the newline and any preceeding spaces)
   is consumed by the processor and the two parts of the field-body
   joined to form a single, logical line.  For example:
   Eulers-Number : 2.718281828459045235360287471
     352662497757247093699959574966967627724076630353547
     5945713821785251664274274663919320030599218174135...

                       Figure 2: Example of Folding

   Note that imposing a line length limit effectively limits the length
   of the field-name, since the field separator MUST appear on the same
   line with the field-name and the field-name MUST NOT be folded.
   Also, when imposing a line length limit, note that some encodings
   (including the Unicode encodings) can use a variable number of bytes
   per character or commonly use more than one byte per character.
   Characters MUST NOT be folded in the middle of a byte sequence.
   Furthermore, folding SHOULD NOT be done just prior to a combining
   character (since this will alter the display of characters in the
   file and might result in unintentional alteration of the file's
   semantics).

   In some cases, the field-body contains spaces that are important to
   the data.  To accurately preserve whitespace in the document, an



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   optional line-continuation character (backslash, %x5C) MAY be
   included to delimit and separate whitespace to be preserved from
   whitespace that will be removed by the processor.  The line-
   continuation character and any whitespace that follows it (including
   whitespace at the beginning of the continuing field-body on the next
   line) MUST be consumed by the processor when reading the file.
   Whitespace appearing before the line-continuation MUST NOT be
   consumed.  Use of the line continuation character makes the
   whitespace visible in the file.

   In other cases, the field-body might contain natural language text,
   and, while it is readily apparent that many languages use spaces to
   separate words, others, such as Japanese or Thai, do not.
   Implementations MAY, in the absence of line continuation characters,
   replace the continuation sequence (the line break and surrounding
   whitespace) in a folded line with a single ASCII space (%x20),
   however, implementations SHOULD just remove the continuation sequence
   altogether in order to avoid causing unnatural breaks in the text.

   Here are some examples:
   SomeField : This is some running text \
    that is continued on several lines \
    and which preserves spaces between \
    the words.
   %%
   AnotherExample: There are three spaces   \
   between 'spaces' and 'between' in this record.
   %%
   SwallowingExample: There are no spaces between \
          the numbers one and two in this example 1\
          2.
   %%

          Figure 3: Example of Folding with Preserved Whitespace

   Note that entirely blank continuation lines are not permitted.  That
   is, this record is illegal, since the field-body of "SomeText" would
   be the empty string:
   %%
   SomeText:               \
                           \
                           \
   %%

                   Figure 4: Whitespace Folding Example






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2.2.  Comments

   Comments MAY be included in the body of the record-jar document by
   placing them at the end of a separator line.  The comment MUST be
   separated by at least one space from the "%%" sequence that
   introduces the separator.

   Multiple separators MAY appear between records.  Logically this
   appears to result in records that contain no fields: records
   containing no fields MUST be ignored by a processor.

   Folding of comments is not permitted; instead multiple comment lines
   MUST be used.  Comments can not appear in the body of a record.  For
   example:
   %% this is a comment.
   Record: goes here
   %%
   %% here is another sequence of comments
   %% that appear on multiple lines
   Record: another record
   %% a final comment
   %%

                         Figure 5: Comment example

2.3.  Characters, Encodings, and Escapes

   By default, a file containing a record-jar archive uses the UTF-8
   character encoding (see [RFC3629]).  If an application, protocol, or
   specification permits an encoding other than UTF-8 to be used in the
   file, it SHOULD also support reading the encoding from the encoding
   signature.  The encoding signature, when present, MUST be the very
   first line of the file.  If the encoding signature is not present, an
   application or protocol MAY attempt to infer the encoding using other
   means.  Record-jar files SHOULD include an encoding signature, even
   if one is not required, whenever the application, protocol, or
   specification permits one.

   A file that uses the UTF-16 or UTF-32 encoding MAY also include a
   Byte Order Mark (U+FEFF) as the first sequence of two octets (in the
   case of UTF-16) or four octets (in the case of UTF-32) in the file,
   just preceeding the encoding signature.

   Some applications, protocols, or specifications require that the
   record-jar file use some other, non-Unicode, legacy character set.
   In particular, some applications, protocols, or specifications only
   support the US-ASCII character set ([ISO646]).




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   Here is an example of the encoding signature for the UTF-8 encoding
   of Unicode:
   %%encoding:UTF-8

                Figure 6: Example of an Encoding Signature

   Printable ASCII characters excepting backslash ("\") and ampersand
   ("&") are represented as themselves.

   Non-ASCII values MAY be included in a record-jar file in several
   ways.  For portability, the best mechanism is to use escape sequences
   in the field-body.  Exclusive use of escape sequences results in a
   pure ASCII text file.

   Non-ASCII characters MAY be represented using the character's Unicode
   value represented using the Numeric Character Reference format
   adapted from XML; the sequence "&#x" (%x26.23.78) is followed by the
   character's Unicode scalar value in hex followed directly by the
   semi-colon character (";", %x3B).  Leading zeroes MAY be omitted.
   For example, the EURO SIGN is U+20AC and could be represented as
   "€".

   Non-ASCII characters MAY also be represented as their associated
   octet sequence in the file's character encoding.  For example, the
   EURO SIGN would be represented as the byte sequence %xE2.82.AC in
   UTF-8.

   The characters for carriage return, newline, and tab when considered
   as part of the data (and not the file format itself) are represented
   by the traditional escape sequences "\r" (%x5C.72), "\n" (%x5C.6E),
   and "\t" (%x5C.74) respectively.  The character backslash is
   represented by "\\" (%x5C.5C), while the ampersand character is
   represented by "\&" (%x5C.26).  A single backslash at the end of a
   line indicates continuation, as discussed in Section 2.1.  Otherwise
   a single backslash followed by some other character in the data is an
   error, although a record-jar processor MAY choose to interpret it as
   a backslash.














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3.  Examples

   Here is the canonical example from [AOUP]:
   Planet: Mercury
   Orbital-Radius: 57,910,000 km
   Diameter: 4,880 km
   Mass: 3.30e23 kg
   %%
   Planet: Venus
   Orbital-Radius: 108,200,000 km
   Diameter: 12,103.6 km
   Mass: 4.869e24 kg
   %%
   Planet: Earth
   Orbital-Radius: 149,600,000 km
   Diameter: 12,756.3 km
   Mass: 5.972e24 kg
   Moons: Luna

   A more complete example showing more of the various features in the
   format is described in [RFC4646].  The data shown here is taken from
   the Language Subtag Registry defined that document:
   %%
   Type: language
   Subtag: ia
   Description: Interlingua (International Auxiliary Language \
     Association)
   Added: 2005-08-16
   %%
   Type: language
   Subtag: id
   Description: Indonesian
   Added: 2005-08-16
   Suppress-Script: Latn
   %%
   Type: language
   Subtag: nb
   Description: Norwegian Bokmål
   Added: 2005-08-16
   Suppress-Script: Latn
   %%










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4.  References

4.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC4234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00
              (work in progress), October 2005,
              <ftp://ftp.rfc-editor.org/in-notes/rfc4234.txt>.

   [UAX31]    Davis, M., "Unicode Standard Annex #31: Identifier and
              Pattern Syntax", 09 2006.

   [Unicode]  Unicode Consortium, "The Unicode Consortium. The Unicode
              Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003.
              ISBN 0-321-49081-0)", January 2007.

4.2.  Informative References

   [AOUP]     Raymond, E., "The Art of Unix Programming", 2003,
              <urn:isbn:0-13-142901-9>.

   [ISO646]   International Organization for Standardization, "ISO/IEC
              646:1991, Information technology -- ISO 7-bit coded
              character set for information interchange.", 1991.

   [RFC4646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for the
              Identification of Languages", September 2006,
              <http://www.ietf.org/rfc/rfc4646.txt>.

















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Appendix A.  Acknowledgements

   Thanks to Eris S. Raymond for his gracious permission to both
   reference and quote The Art of Unix Programming in this document.
   Without his work, this document would likely not exist.

   Contributors to this document include: Stephane Bortzmeyer, John
   Cowan, Frank Ellerman, Doug Ewell.

   The IETF LTRU working group adopted record-jar format on John Cowan's
   suggestion.  That effort required record-jar to be documented and
   many people in that group contributed to this work there: the author
   thanks everyone who participated in that effort, even though names
   cannot be mustered here.





































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Author's Address

   Addison Phillips (editor)
   Yahoo! Inc.

   Email: addison@inter-locale.com
   URI:   http://www.inter-locale.com












































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