Movatterモバイル変換

Network Working Group                                     N. BorensteinRequest for Comments: 1437                                     Bellcore                                                             M. Linimon                                       Lonesome Dove Computing Services                                                           1 April 1993The Extension of MIME Content-Types to a New MediumStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard.  Distribution of this memo is   unlimited.Abstract   A previous document,RFC 1341, defines a format and general framework   for the representation of a wide variety of data types in Internet   mail.  This document defines one particular type of MIME data, the   matter-transport/sentient-life-form type.  The matter-   transport/sentient-life-form MIME type is intended to facilitate the   wider interoperation of electronic mail messages that include entire   sentient life forms, such as human beings.   Other informally proposed subtypes, such as "non-sentient-life-form",   "non-sentient-non-life-form", and the orthogonally necessary but   nevertheless puzzling "sentient-non-life-form", are not described in   this memo.The matter-transport/sentient-life-form MIME type   In order to promote the wider interoperability of life-bearing email,   this document defines a new MIME content-type, "matter-transport",   and for an initial subtype, "sentient-life-form".  This subtype was   designed to meet the following criteria:      1.  The syntax must be extremely simple to parse, to minimize the      risk of accidental death due to misinterpretation of the standard.      2.  The data format must be extremely robust, with redundancy to      ensure that individual life forms will survive and be      reconstituted in such a form as to be nearly indistinguishable      from their initial state, no matter how many bizarre email      gateways are encountered in transit.      3.  The syntax must be extensible to allow for the description of      all yet-undiscovered aspects of life forms which will be requiredBorenstein & Linimon                                            [Page 1]

RFC 1437          MIME Content-Types for a New Medium       1 April 1993      for the transport of non-human species (e.g. dolphins, Klingons,      or politicians).      4.  The syntax must be compatible with SGML, so that with an      appropriate DTD (Document Type Definition -- the standard      mechanism for defining a document type using SGML), a general SGML      parser could be written to parse the data structure and produce      directives to a lifeform-reconstitution mechanism. However,      despite this compatibility, the syntax will most likely be far      simpler than that of full SGML (so that no SGML knowledge is      required in order to implement it), since it is anticipated that      the full complexities of SGML will not be necessary for the      description of even arbitrarily complex organic life forms.   The syntax of the new content-type is very simple, and indeed makes   considerable sacrifice of efficiency in the interest of simplicity.   It is assumed to describe a three-dimensional rectangular solid, with   the height, width, and depth (calibrated in centimeters) specified as   parameters on the content-type line.  (In general, this should be a   cube that completely contains the life form being transported; but,   where high bandwidth is not available, a somewhat smaller cube can be   used, provided that facilities are known to be available at the   recipient's end to administer the medical first aid that could be   necessary if an individual is reconstituted sans some of its   extremities.)  A fourth parameter gives the resolution of the matter   scan, calibrated in Angstroms.  Thus, the following Content-type   value:      Content-type:  matter-transport/sentient-life-form;              height = 200; width = 60; depth=60; resolution=10   implies that the cube being described is 60 cm by 60 cm by 200 cm,   and is described to a resolution of 10 Angstroms.  The resolution   gives the quantization unit, and therefore determines the quality of   the reproduction.  The data stream itself then consists of a readout   of the molecule found at each location, using the given resolution.   If the resolution is high enough that more than one molecule is found   in a given location, the molecule whose nucleus is closest to the   center of the cube is used.  Each molecule is described by its   molecular formula, rendered in ASCII for maximum readability if   matter-transport mail is inadvertently delivered to a human recipient   and displayed on a terminal screen.  Each molecule is followed by a   space (ASCII 32) to separate it from the subsequent molecule   description.  Extremely long molecules may require the use of a   content-transfer-encoding such as quoted-printable, to ensure that   line-wrapping mail systems do not, for example, cause the unintended   breakdown of complex proteins into their constituent elements.Borenstein & Linimon                                            [Page 2]

RFC 1437          MIME Content-Types for a New Medium       1 April 1993   The following is a message that gives a somewhat simplified rendition   of a well-known American politician, starting from the top:   From:  "Nathaniel S. Borenstein" <nsb@bellcore.com>   To: Mark Linimon <linimon@lonesome.com>   Subject: Think hard before reconstructing   Content-description:  Dan Quayle, low-res version   Content-type: matter-transport/sentient-life-form           height = 200; width = 60; depth=60; resolution=100000   Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe  Fe   Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe  Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 Fe   Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe  Fe   Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe  Fe   Obviously, a real politician's skull is more complex than pure iron,   as is its interior, but this simplified example should give the   general flavor of the protocol.   (A caveat, however, in the reconstitution of Vice-Presidents of the   United States: allegedly, some of the matter-reconstitution schemes   currently under development are reputed to perform less than   optimally while trying to reconstitute areas of relatively high   vacuum; for instance, their skulls.  A recommended acceptance test   might be to experiment with subjects whose skulls are only at partial   vacuum, such as Vice-Presidents of Marketing.)MHS (X.400) Gateway Considerations   The proper behavior of a MIME/MHS gateway with regard to the   transmission of complex multimedia messages is a topic of ongoing   investigation under the auspices of the IETF.  The addition of matter   transport should not significantly complicate that effort, as it is   already necessary to specify gateway behavior for MIME types that   have no X.400 equivalents, and matter transport is simply anotherBorenstein & Linimon                                            [Page 3]

RFC 1437          MIME Content-Types for a New Medium       1 April 1993   such untranslatable type.   However, real-world X.400 gateways might be considered to   significantly increase the hazard that mail containing a human being   will be rejected with a message so cryptic that the recipient deletes   it without ever realizing that an embedded human being is enclosed.   For this reason, it is recommended that the subject of matter   transport be explicitly marked "for further study" in the next   generation of the X.400 specification, X.400-1996.  This will give   the community ample time to define a more complete specification for   matter transport as part of X.400-2000, and possibly even a readily-   implementable specification as part of X.400-2004, although some will   no doubt argue that this would be too strong a break with tradition.Implementation Considerations   The user is cautioned against passing MIME transporter messages   through computers equipped with the NFS file system.  A no-file space   error caused one of the laboratory rats on our prototype system to be   truncated to a zero-length file.  Unfortunately we had neglected to   mount a scratch rat.  (We have decided to permanently retain the   empty filename in his honor).   Byte swapping problems on other storage systems can be similarly   annoying, but should not be a problem if network byte order is always   maintained ocrrcelty.   Despite the authors' belief in the robustness of the protocol,   passage of email through certain systems seems to result in the   sentient-life-form arriving at its destination upside down, resulting   in an annoying "thud".  The cause is still under investigation.   Interoperation with matter-transporters using polar coordinate   systems is discouraged, due to round-off and other algorithmic errors   in certain ubiquitous floating-point implementations, leading to   results which are best discreetly described as "disappointing."   Similarly, off-by-one errors should be avoided.   Widespread adoption of this protocol may lead to an increase in user   demand for reliable backup systems.  More importantly, for the first   time management may be motivated to adequately fund such systems when   they discover the possibility that proper email backup may confer   upon them virtual immortality.  (On the other hand, implementors   should seriously consider the desirability of making their managers   immortal.)Borenstein & Linimon                                            [Page 4]

RFC 1437          MIME Content-Types for a New Medium       1 April 1993   An additional concern reflects the fact that, prior to the   introduction of this content-type, duplicate mail delivery was a   relatively minor nuisance.  With the mail extensions described in   this document, however, comes the possibility that duplicate mail   delivery will leave a user with, for example, multiple spouses or   mothers-in-law.  The relative weights of the desire to avoid   duplicate delivery and the desire to avoid lost mail may change   accordingly.Security Considerations   Security considerations are not discussed in this memo.  However, law   enforcement officials might wish to consider the possibility that   this mechanism could be used by criminals, either to escape   extradition by mailing themselves outside of a legal jurisdiction, or   to outwait the statute of limitations by mailing themselves through   complex mail routes with long delays.  (One supposes that they could   also look on the bright side, and consider MIME as a possible   approach to solving the long-standing problem of prison   overcrowding.)Authors   The authors of this document may be reconstituted by feeding the   following data to an Internet-connected MIME reader:Content-type: multipart/mixed; boundary=NextAuthor--NextAuthorContent-type: message/external-body; access-type=anon-ftp;        site=thumper.bellcore.com; directory=pub/nsb; name=nsb.fleshContent-Description: Nathaniel BorensteinContent-type:  matter-transport/sentient-life-form        height = 200; width = 60; depth=60; resolution=100000--NextAuthorContent-type: message/external-body; access-type=anon-ftp;        site=thumper.bellcore.com; directory=pub/nsb; name=linimon.fleshContent-Description: Mark LinimonContent-type:  matter-transport/sentient-life-form        height = 200; width = 60; depth=60; resolution=100000--NextAuthor--Borenstein & Linimon                                            [Page 5]

RFC 1437          MIME Content-Types for a New Medium       1 April 1993Authors' Addresses   Nathaniel Borenstein   Bellcore Room MRE 2D-296   445 South Street   Morristown, NJ 07962-1910   Phone: (201) 829-4270   EMail: nsb@bellcore.com   Mark Linimon   Lonesome Dove Computing Services   P.O. Box 20291   Roanoke, VA 24018   Phone: (703) 776-1004   EMail: linimon@LONESOME.COMBorenstein & Linimon                                            [Page 6]