rfc2122.txt

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   password:       [e-mail]  {user prompted for password}
   401 Unauthorized                {an anonymous user is not allowed to
                                    access the service}

   d) Some services may use additional data transmitted in the parameter
      fields, for example:
        URL: vemmi://mctel.fr/demo;$USERDATA=smith;account=1234
      If no access check is done by the host, the dialog might be:
   service:        demo;$USERDATA=smith;account=1234
   200 OK
    ...starting VEMMI session...

7)  Procedure to use when a VEMMI URL is encountered in a HTML document
    without VEMMI support:

   The VEMMI URL support may be built-in in some Web browsers, or
   offered by an associated software or plug-in interworking with the
   user browser, for example using the WWW_RegisterProtocol API command
   to register the new VEMMI protocol.

   When a Web browser encounters a VEMMI URL without having VEMMI support,
   two cases may occur:
   - some browsers will detect an unrecognized scheme and signal an
     unrecoverable error directly.



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   - others will manage it as a relative URL [4] and will build a
     complete URL including the VEMMI URL and will request it from the
     host having sent the current document. In this case the host will
     usually return the error "not found".

   Among the mechanisms that could be used in order to offer a friendly
   interface to both users with and without VEMMI support:
   - when the second case occurs and the relative URL including the
     vemmi:// string is transmitted to the server, the HTTPD server may
     be modified in order to recognize such URL and to propose the
     downloading of a VEMMI client software.
   - the HTML document including the vemmi URL allowing to start the
     VEMMI session may propose both options, for example:
        If your browser supports VEMMI, directly
        <A HREF="vemmi://ares.mctel.fr/TEST">start the interactive
        multimedia service</A>, otherwise
        <A HREF="ftp://ftp.mctel.fr/vemmi.exe">download first a VEMMI
        client software</A>.
   - the application/vemmi MIME type is defined below (to allow for
     example exchange of vemmi objects). A possible way is for the
     server to look in the HTTP Accept header field and to deduce that if
     application/vemmi is supported, then the VEMMI support exists (in
     this case, application/vemmi is to be defined in the browser and
     associated with the vemmi decoder).

8) Security Considerations:

   The VEMMI URL scheme is subject to the same security implications as
   the general URL scheme [5] [14], so the usual precautions outlined in
   [5] [14] apply (for example, it is not allowed to store the username
   and password in the URLs).

   Furthermore, among VEMMI objects that could be used during the
   interactive session, metacode objects (representing a sequence of
   VEMMI commands) and operative objects (they are executable programs
   to be run on the client platform) may be downloaded and/or started.

   In order to protect the user against the activation of an harmful
   operative object, it is strongly recommended that the users use the
   configuration menu of their VEMMI software to disable the option of
   running operative objects when receiving potentially unsafe VEMMI
   objects, or at least enable the option to request first user approval
   before starting the execution of an operative object.

   The VEMMI remote interactive services may vary widely in their access
   control policies; in practice, when a prompt for username or password
   is received, the VEMMI terminal should request them from the user.
   The VEMMI terminal implementation could support additional features,



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   for example proposing by default "anonymous" as username and the user
   Internet e-mail address as password, or looking in an encrypted local
   database for user identification on this service.

   Such an identification mechanism using the username/password scheme
   is unsecure and is provided for backwards compatibility only. The
   VEMMI services requiring a safe identification procedure must rely on
   other alternative mechanisms (e.g. S/KEY or other). In numerous
   cases, the user identification procedure will be performed by the
   VEMMI service.

9) application/vemmi MIME type

   VEMMI is a multimedia interactive service and VEMMI objects are
   usually exchanged through a continuous VEMMI multimedia session.
   However, VEMMI objects could also be transmitted and exchanged using
   other mechanisms, for example using HTTP, through e-mail, and so
   on... The assignment of a MIME media type application/vemmi will
   allow this transport and exchange of VEMMI objects, and this
   paragraph describes this MIME type.

   Furthermore, for Web browsers not supporting the addition of new URL
   protocol scheme, the VEMMI MIME type may also be used to transmit,
   instead of a VEMMI object, a text file containing the VEMMI URL to
   activate to connect to a VEMMI server.

9A) DESCRIPTION:

   MIME media type name: "application"

   MIME subtype name: "vemmi"

   Required parameters: none

   Optional parameters:
   - version:
     an optional version number may be specified, in the format:

       version=<integer>

     The version number is a numeric integer whose is encoded as the
     <version> parameter defined in ETS 300 709 (e.g. version=100), and
     whose the first digit represents the major VEMMI version number.
     It must be pointed out that the VEMMI objects includes the VEMMI
     version and a timestamp.






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9B) ENCODING CONSIDERATIONS:

   The "base64" mechanism is preferred because VEMMI use a native 8-bit
   binary file format. However, as VEMMI includes its own 7-bits
   encoding mechanisms, VEMMI data could also be transmitted in 7-bit
   mode.

9C) SECURITY CONSIDERATIONS:

   Refer to paragraph 8.

9D) INTEROPERABILITY CONSIDERATIONS:

   VEMMI is designed to be fully platform independent, and the VEMMI
   objects and contents could interoperate between any platform. The
   only exception are the VEMMI operative objects that could be binary
   programs specific to a given hardware platform and operating system.

10) Liaison address:

   For all technical questions regarding this request, please contact:

           Daniel Mavrakis
           Monaco Telematique MC-TEL
           P.O. Box 225
           MC 98004 Monte-Carlo Cedex
           PRINCIPALITY OF MONACO
           EMail: [e-mail]
           Tel: [phone]
           Fax: [phone]

   Comments may also be addressed to:

           Mr. Herve Layec,
           ETSI STC TE1
           06921 SOPHIA ANTIPOLIS Cedex
           FRANCE
           EMail: [e-mail]
           Tel: [phone]
           Fax: [phone]











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           Mr. Kurt Kartmann
           Consulting
           Telecommunication+Multimedia
           Gabelsbergerstr. 2
           D-64807 DIEBURG
           GERMANY
           EMail: [e-mail]
           Tel: [phone]
           c/o Deutsche Telekom AG
           Tel. [phone], Fax [phone]

   The authors thank the other members of the ETSI TE1 VEMMI Working
   Group for their comments:

      - Michael Blaschitz ([e-mail])
      - Agnelo Fernandes ([e-mail])
      - Daniel Allonsius ([e-mail])
      - Stefaan Herrebout ([e-mail])
      - Francisca Oliva ([e-mail])
      - Herwart Wermescher ([e-mail])

11) References:

   [1] "Enhanced Man-Machine Interface for Videotex and
       Multimedia/Hypermedia Information Retrieval Services (VEMMI
       revision 1)", ETS 300 709 standard (European Telecommunications
       Standards Institute), September 1996.
       This document is available on the Web in HTML format: see
       http://www.etsi.fr/ecs/projects/vemmi/vemmi.htm

   [2] "Enhanced Man-Machine Interface for Videotex and Other
       Information Retrieval Services (VEMMI)", ITU-T T.107 standard
       (International Telecommunications Union), March 1995.

   [3] "Videotex Enhanced Man-Machine Interface service (VEMMI)",
       ETS 300 382 standard (European Telecommunications Standards
       Institute), February 1995.

   [4] Fielding, R., "Relative Uniform Resource Locators", RFC 1808, UC
       Irvine, June 1995.

   [5] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform Resource
       Locators (URL)", RFC 1738, December 1994.

   [6] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
       October 1994.





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   [7] Mavrakis, D., "VEMMI and Internet", TD 44, ETSI TE1 plenary
       meeting in Brussels, October 20, 1995.

   [8] Berners-Lee, T., Fielding, R., and H. Frystyk: "Hypertext Transfer
       Protocol - HTTP/1.0", RFC 1945, MIT/LCS, UC Irvine, May 1996.

   [9] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
       Berners-Lee, Transfer Protocol - HTTP/1.1", RFC 2068, UC Irvine,
       January 1997.

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

   [11] Masinter, L., Zigmond, D., and H. Alvestrand, "Guidelines and
        Process for new URL Schemes", Work in Progress.

   [12] Berners-Lee, T., and D. Connolly, "Hypertext Markup Language
        Specification - 2.0", RFC 1866, MIT/LCS, November 1995.

   [13] "Port Numbers",
        ftp://venera.isi.edu/in-notes/iana/assignments/port-numbers

   [14] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource
        Locators (URL)", Work in Progress.


























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