The Application/CALS-1840 Content-type
Mailing military technical documents through email
Levinson, E., "The Application/CALS-1840 Content-type", RFC 1895, DOI 10.17487/RFC1895, February 1996, <https://www.rfc-editor.org/info/rfc1895>.
@misc{rfc1895,
series = {Request for Comments},
number = 1895,
howpublished = {RFC 1895},
publisher = {RFC Editor},
doi = {10.17487/RFC1895},
url = {https://www.rfc-editor.org/info/rfc1895},
author = {E. Levinson},
title = {{The Application/CALS-1840 Content-type}},
pagetotal = 6,
year = 1996,
month = feb,
} RFC text
Contents
Network Working Group E. Levinson
Request for Comments: 1895 Accurate Info. Sys., Inc.
Category: Informational February 1996
The Application/CALS-1840 Content-type
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This memorandum provides guidelines for using the United States
Department of Defense Military Standard MIL-STD-1840, "Automated
Interchange of Technical Information," with the Internet electronic
mail standards, RFC 822 and RFC 1521. Electronic mail provides a
more convenient mechanism that delivery via physical media for
certain types and quantities of data. Software already exists to
support data exchanges based on MIL-STD-1840 and it can continue to
be used in conjunction with electronic mail exchanges defined in this
document. This document defines a new media type and a MIME message
structure for exchanging data in conformance with MIL-STD-1840.
1. Introduction
The United States Department of Defense (DOD) has defined a standard,
MIL-STD-1840 [1840], for the exchange of digital data. Most
applications of that standard use 9-track tape as the transport
medium. The Application/CALS-1840 media-type is proposed to
facilitate such exchanges using the Multipurpose Internet Mail
Extensions [MIME] and network based transport media, i.e. electronic
mail [822].
This memo has been reviewed and authorized by the Continuous
Acquistion and Life-cycle Support (CALS) Industry Steering Group
(ISG). CALS is a US DOD initiative for the use and exchange of
digital data. The Industry Steering Group, which consists of members
drawn from government and industry, guides the development of CALS
standards such as [1840].
2. Definition
An [1840] exchange consists of a set of files with well defined file
names (see below). Each set consists of a declaration file and one
or more data files. The data files, in turn, consist of header
records immediately followed by the data. The data itself may be
formatted in accordance with a published specification or a
contractual agreement.
MIL-STD-1840 encodes the file's data type in the file name.
It might seem appropriate to transform the 1840 headers into MIME
headers and use the appropriate media type, essentially transforming
the 1840 files into MIME body parts. There are three reasons for not
doing that. First, not all of the "types" used in [1840] are
registered MIME types. Second, there exists an installed base of
software capable of reading the 1840 formatted files and processing
the data appropriately. Finally the three existing revisions to the
standard have maintained the same file structure. Consequently, a
processor for the data may be able to handle any one of the
standard's revisions. Thus, a single Application/CALS-1840 is being
proposed and its body part body contains headers and data in the
[1840] format.
A set of related files constitutes a "transfer unit" in 1840 and each
transfer unit shall correspond to a Multipart/Mixed MIME entity.
Included in each transfer unit is a declaration file which shall be
the first body part in the Multipart/Mixed entity. Several transfer
units may be included in a single MIME message.
2.1 Registration Information
The following form is copied from RFC 1590, Appendix A for the
purpose of registering this media-type.
To: IANA@isi.edu
Subject: Registration of new Media Type content-type/subtype
Media Type name: Application
Media subtype name: CALS-1840
Required parameters: filename, version
Optional parameters: None
Encoding considerations: Any valid MIME encodings my be used
Security considerations: Depends solely on the referenced type
Published specification: This document
Person & email address
to contact for further
information: Alan Peltzman <peltzmaa@ncr.disa.mil>
+1 (703) 735-3568
Defense Information Systems Agency
Center for Standards
Code JIEO/JEBEB
10701 Parkridge Blvd
Reston, VA 22091-4398
2.2. The Filename Parameter
The filename parameter gives the transfer unit filename as defined by
[1840]. The parameter's value, called <1840-name>, has the syntax
given by the grammer below.
1840-name := "D" 1840-tuseq [ 1840-type 1840-dfseq ]
1840-type := letter ; limited to the set defined in
; the appropriate version of
; [1840, Table III]
1840-tuseq := 1840-seq
1840-dfseq := 1840-seq
1840-seq := alphnum alphnum alphnum
alphanum := letter / digit
letter := "A" / "B" / "C" / "D" / "E" / "F" / "G" /
"H" / "I" / "J" / "K" / "L" / "M" / "N" /
"O" / "P" / "Q" / "R" / "S" / "T" / "U" /
"V" / "W" / "X" / "Y" / "Z"
digit := "0" / "1" / "2" / "3" / "4" / "5" /
"6" / "7" / "8" / "9" /
All Application/CALS-1840 body parts in a single Multipart/Mixed MIME
entity shall have the same <1840-tuseq>. Within a single message all
filename values shall be unique.
Notes: 1) Tuseq and dfseq correspond to transfer unit sequence number
and data file sequence number respectively. 2) The filename for a
declaration file has the form "D" 1840-tuseq and for data files, the
form "D" 1840-tuseq <letter> 1840-dfseq.
2.3. The Version Parameter
The specversion parameter's value shall indicate the particular
version of MIL-STD-1840 to which the data conforms. Valid values
are:
MIL-STD-1840C, 0, 199XXXXX
MIL-STD-1840B, 0, 19921103
MIL-STD-1840A, 0, 19871222
Notes: (1) The value "199XXXXX" is to be replaced with the actual
issue date for MIL-STD-1840C. (2) The embedded blanks in the above
strings are required, hence the value must be enclosed in quote marks
(").
3. Example
In the example below a single transfer unit is provided. It consists
of three data files, the declaration, a contract defined file and an
IGES file. The headers and data are in accordance with MIL-STD-
1840B. The content-transfer-encoding perserves the data file's fixed
record length.
To: you@some.org
From: me@here.com
Date: Fri, 03 Nov 1995 18:23:10 -0500
MIME-Version: 1.0
Content-Type: Multipart/Mixed;
Boundary="DISA CFS - SFC ASID"
--DISA CFS - SFC ASID
Content-Type: Application/CALS-1840; filename=D001;
version="MIL-STD-1840B, 0, 19921103"
Content-Transfer-Encoding: Base64
[Declaration File]
--DISA CFS - SFC ASID
Content-Type: Application/CALS-1840; filename=D001A001;
version="MIL-STD-1840B, 0, 19921103"
Content-Transfer-Encoding: Base64
[Data File -- Contract Defined including headers]
--DISA CFS - SFC ASID
Content-Type: Application/CALS-1840; filename=D001Q001;
version="MIL-STD-1840B, 0, 19921103"
Content-Transfer-Encoding: Base64
[Data File -- Raster including 1840 headers]
--DISA CFS - SFC ASID--
4. Security Considerations
None of the body parts, as constitued, represent executable data.
When the 1840 file format is processed the resultant data may be
executable. Processing will be under the control of the process
associated with Application/CALS-1840.
Classified information or other information that cannot be disclosed
except to authorized personnel should not be sent via the Internet
without using appropriate privacy enhancements, [PEM], [MOSS], or
other privacy mechanism.
5. Acknowledgments
The author acknowledges the encouragement of Alan Peltzman, US DOD,
DISA, and the suggestions of Richard Klobuchar, SAIC.
This work was supported under U.S. Dept. of the Army, Contract
DAAB07-93-D-T001 and prepared under the direction of the MIL-STD-1840
Revision C Review Team.
6. References
[1840] MIL-STD-1840B, "Automated Interchange of Technical
Information", US Department of Defense, 3 November 1992.
[822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, UDEL, August 1982.
[MIME] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet
Mail Extensions): Mechanisms for Specifying and
Describing the Format of Internet Message Bodies", RFC
1521, Bellcore and Innosoft, September 1993.
[MOSS] Crocker, S., Freed, N., Galvin, J., and S. Murphy, "MIME
Object Security Services", RFC 1848, Cybercash, Innosoft,
TIS, October 1995.
[PEM] Linn, J., "Privacy Enhancement for Internet Electronic Mail:
Part I: Message Encryption and Authentication Procedures",
RFC 1421, IAB IRTF PSRG, IETF PEM WG, February 1993.
9. Author's Address
Edward Levinson
Accurate Information Systems, Inc.
2 Industrial Way
Eatontown, NJ 07724-2265
USA
Phone: +1 908 389 5550
EMail: ELevinson@Accurate.com
AI ELI5
On this page
§1Introduction
MIL-STD-1840 is the United States Department of Defense standard for exchanging digital data. Traditionally, this data was transported on 9-track magnetic tape, but email offers a more convenient mechanism for many applications. The Application/CALS-1840 MIME media type enables MIL-STD-1840 data exchanges using Internet email as the transport mechanism instead of physical media.
This RFC was reviewed and authorized by the Continuous Acquisition and Life-cycle Support (CALS) Industry Steering Group, which guides the development of CALS standards including MIL-STD-1840.
The military needed a way to send technical blueprints and documents through email. This RFC explains how to do that using a special label.
§2MIL-STD-1840 Data Structure
An MIL-STD-1840 exchange consists of a set of files with well-defined file names. Each set contains a declaration file (which describes the contents) followed by one or more data files. The data files contain header records immediately followed by the actual data, which may be formatted according to published specifications or contractual agreements.
Rather than transforming 1840 files into separate MIME body parts, the RFC preserves the 1840 file format as-is. This approach has three advantages: many file types used in 1840 are not registered MIME types; there is existing software capable of reading 1840 formatted files; and three revisions of the standard have maintained the same file structure, so a single processor may handle any revision.
A military document set has a cover sheet that lists what's inside, then the actual documents. We keep them in their original military format instead of changing them for email.
§3MIME Implementation
A set of related files constitutes a transfer unit in MIL-STD-1840, and each transfer unit shall correspond to a Multipart/Mixed MIME entity. The declaration file must be the first body part in the Multipart/Mixed entity. Several transfer units may be included in a single MIME message, and each Application/CALS-1840 body part requires two parameters: filename and version.
The filename parameter gives the transfer unit filename as defined by the military standard. The filename has a specific syntax: it begins with the letter D, followed by a three-character transfer unit sequence, optionally followed by a type letter and a three-character data file sequence. All Application/CALS-1840 body parts in a single Multipart/Mixed entity must share the same transfer unit sequence.
When you send the military documents through email, you group them together and put a special label on each one that says what version of the military standard it uses.
§4Version Parameter and Example
The version parameter indicates which version of MIL-STD-1840 the data conforms to. Valid values include MIL-STD-1840C, MIL-STD-1840B (dated 19921103), and MIL-STD-1840A (dated 19871222). Each revision maintains the same fundamental file structure, allowing processing software to handle data from multiple versions.
The RFC includes a complete example showing a single transfer unit with three data files: a declaration file, a contract-defined file, and an IGES file. The headers and data conform to MIL-STD-1840B, and the content is base64 encoded for email transmission. This example demonstrates how a real military data exchange would be packaged for email delivery.
You tell the receiver which version of the military standard you used, so they know what software to use to read it.