RFC1895 - The Application/CALS-1840 Content-type

领测软件测试网

　　 
　　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, RFC822 and RFC1521. 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 RFC1590, 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, RFC822, 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", RFC1848, Cybercash, Innosoft,
TIS, October 1995.

[PEM] Linn, J., "Privacy Enhancement for Internet Electronic Mail:
Part I: Message Encryption and Authentication Procedures",
RFC1421, 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

文章来源于领测软件测试网 https://www.ltesting.net/