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Versions: 00 01 02 03 04 05 RFC 4709

Network Working Group                                         J. Reschke
Internet-Draft                                                greenbytes
Expires: February 8, 2006                                 August 7, 2005


   Mounting WebDAV (Web Distributed Authoring and Versioning) servers
                     draft-reschke-webdav-mount-00

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document specifies a mechanism and a document format that
   enables Web Distributed Authoring and Versioning (WebDAV) servers to
   send "mounting" information to a WebDAV client.  The protocol is
   designed to work on any platform and with any combination of browser
   and WebDAV client, relying solely on the well-understood dispatch of
   documents through their MIME type.

Editorial Note (To be removed by RFC Editor before publication)




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   Please send comments to the Distributed Authoring and Versioning
   (WebDAV) working group at <mailto:w3c-dist-auth@w3.org>, which may be
   joined by sending a message with subject "subscribe" to
   <mailto:w3c-dist-auth-request@w3.org>.  Discussions of the WEBDAV
   working group are archived at
   <http://lists.w3.org/Archives/Public/w3c-dist-auth/>.

   Note that although discussion takes place on the WebDAV working
   group's mailing list, this is not a working group document.

   XML versions, latest edits and the issues list for this document are
   available from
   <http://greenbytes.de/tech/webdav/#draft-reschke-webdav-mount>.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Format . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1   dm:mount . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2   dm:url . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.3   dm:open  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.4   dm:username  . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   5.  Internationalization Considerations  . . . . . . . . . . . . .  5
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
     6.1   MIME type registration . . . . . . . . . . . . . . . . . .  5
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     8.1   Normative References . . . . . . . . . . . . . . . . . . .  7
     8.2   Informative References . . . . . . . . . . . . . . . . . .  7
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  8
   A.  Alternative approaches . . . . . . . . . . . . . . . . . . . .  8
     A.1   ...through HTML/CSS extensions . . . . . . . . . . . . . .  8
     A.2   ...through custom URI schemes  . . . . . . . . . . . . . .  8
       Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
       Intellectual Property and Copyright Statements . . . . . . . . 10














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1.  Introduction

   By definition, a WebDAV server ([RFC2518]) is an HTTP server as well
   ([RFC2616]).  Most WebDAV servers can be (at least partly) operated
   from an HTML-based user interface in a web browser.  However, it is
   frequently desirable to be able to switch from an HTML-based view to
   a presentation provided by a native WebDAV client, directly
   supporting the authoring features defined in WebDAV and related
   specifications.

   For completeness, Appendix A lists other approaches that have been
   implemented in existing clients.


2.  Terminology

   The terminology used here follows and extends that in the WebDAV
   Distributed Authoring Protocol specification [RFC2518].

   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].

   This document uses XML DTD fragments ([XML]) as a purely notational
   convention.  In particular:

   o  Element names use the namespace
      "http://purl.org/NET/webdav/mount".  When an XML element type in
      this namespace is referenced in this document outside of the
      context of an XML fragment, the string "dm:" will be prefixed to
      the element name.

   o  Element ordering is irrelevant.

   o  Extension elements/attributes (elements/attributes not already
      defined as valid child elements) may be added anywhere, except
      when explicitly stated otherwise.


3.  Format

   A WebDAV mount request is encoded in a specific XML format ([XML])
   with a well-defined MIME type (see Section 6.1).  The MIME type
   allows user agents to dispatch the content to a handler specific to
   the system's WebDAV client.

   The elements defined below use the namespace
   "http://purl.org/NET/webdav/mount".



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   <!ELEMENT mount (url, open?, username?) >

   <!ELEMENT url (#PCDATA) >
   <!-- PCDATA value: scheme ":" hier-part, as defined in section 3 of
        [RFC3986] -->

   <!ELEMENT open (#PCDATA) >
   <!-- PCDATA value: path, as defined in section 3 of
        [RFC3986] -->

   <!ELEMENT username (#PCDATA) >


3.1  dm:mount

   The <dm:mount> element acts as container for all the remaining
   elements defined by this protocol.

3.2  dm:url

   The mandatory <dm:url> element provides the HTTP URL of the WebDAV
   collection that should be mounted by the client.

3.3  dm:open

   The optional <dm:open> element instructs the client to display the
   specified child collection; it's URL is computed by concatenating
   this element's value with the URL obtained from the <dm:url>
   (Section 3.2) element.

3.4  dm:username

   The server can use the optional <dm:username> element to specify the
   name of the authenticated principal.  A client can use this value to
   select a matching mount point (different users may have mounted the
   URL with different credentials under different local mount points) or
   to provide a meaningful default for a authentication dialogue.

4.  Example

   In the example below, the server instructs the user agent to mount
   the WebDAV URL "http://www.example.com/documents" in it's WebDAV
   client, and then to display the contents the child collection
   "/user42/inbox", identified by the URL
   ""http://www.example.com/documents/user42/inbox".






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   >> Request:

   GET /Coll/&mount-me HTTP/1.1
   Host: www.example.com

   >> Response:

   HTTP/1.1 200 OK
   Content-Type: application/davmount+xml
   Content-Length: xxx

   <dm:mount xmlns:dm="http://purl.org/NET/webdav/mount">
     <dm:url>http://www.example.com/documents</dm:url>
     <dm:open>/user42/inbox</dm:open>
   </dm:mount>


5.  Internationalization Considerations

   This document does not introduce any new internationalization
   considerations beyond those discussed in [RFC2518], Section 16.

6.  IANA Considerations

6.1  MIME type registration

   MIME media type name:

      application

   MIME subtype name:

      davmount+xml

   Mandatory parameters:

      none

   Optional parameters:

      "charset": This parameter has identical semantics to the charset
      parameter of the "application/xml" media type as specified in
      [RFC3023].

   Encoding considerations:

      Identical to those of "application/xml" as described in [RFC3023],
      section 3.2.



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   Security considerations:

      As defined in this specification.  In addition, as this media type
      uses the "+xml" convention, it shares the same security
      considerations as described in [RFC3023], section 10.

   Interoperability considerations:

      There are no known interoperability issues.

   Published specification:

      This specification.

   Additional information:

      Magic number(s):

         As specified for "application/xml" in [RFC3023], section 3.2.

      File extension:

         .davmount

      Fragment identifiers:

         As specified for "application/xml" in [RFC3023], section 5.

      Base URI:

         As specified in [RFC3023], section 6.

      Macintosh File Type code:

         TEXT

   Person and email address to contact for further information:

      Julian Reschke <julian.reschke@greenbytes.de>

   Intended usage:

      COMMON

   Author/Change controller:

      IESG




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7.  Security Considerations

   All security considerations connected to HTTP/WebDAV and XML apply
   for this specification as well, namely [RFC2518] (Section 17) and
   [RFC3470] (Section 7).

   In addition, client implementors must be careful when implementing
   the <dm:open> element (see Section 3.3).  It MUST NOT be used to
   initiate any action beyond displaying the contents of a WebDAV
   collection.

8.  References

8.1  Normative References

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

   [RFC2518]  Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D.
              Jensen, "HTTP Extensions for Distributed Authoring --
              WEBDAV", RFC 2518, February 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3023]  Murata, M., St.Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Third
              Edition)", W3C REC-xml-20040204, February 2004,
              <http://www.w3.org/TR/2004/REC-xml-20040204>.

8.2  Informative References

   [RFC3470]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for
              the Use of Extensible Markup Language (XML) within IETF
              Protocols", RFC 3470, BCP 70, January 2003.

   [WEBARCH]  Walsh, N. and I. Jacobs, "Architecture of the World Wide
              Web, Volume One", W3C REC REC-webarch-20041215,
              December 2004,
              <http://www.w3.org/TR/2004/REC-webarch-20041215/>.



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Author's Address

   Julian F. Reschke
   greenbytes GmbH
   Salzmannstrasse 152
   Muenster, NW  48159
   Germany

   Phone: +49 251 2807760
   Fax:   +49 251 2807761
   Email: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/

Appendix A.  Alternative approaches

A.1  ...through HTML/CSS extensions

   Microsoft Internet Explorer implements a CSS extension that allows
   switching to it's own WebDAV client ("Webfolder", see <http://
   msdn.microsoft.com/workshop/author/behaviors/reference/behaviors/
   anchor.asp>).  However, at the time of this writing this extension
   was not implemented by any other user agent.

A.2  ...through custom URI schemes

   The "kio" library of the "K Desktop Enviroment"
   (<http://www.kde.org/>) uses the URI scheme "webdav" to dispatch to
   the system's WebDAV client.  This URI scheme is not registered, nor
   supported on other platforms.  Furthermore, W3C's "Architecture of
   the World Wide Web, Volume One" explicitly advises against defining
   new schemes when existing schemes can be used:

      "A specification SHOULD reuse an existing URI scheme (rather than
      create a new one) when it provides the desired properties of
      identifiers and their relation to resources."

   (see [WEBARCH], Section 2.4)














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Index

   A
      application/mount
         xml MIME type  5

   D
      dm:mount  4
      dm:opent  4
      dm:url  4
      dm:username  4

   M
      MIME type
         application/mount  5




































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Intellectual Property Statement

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   Intellectual Property Rights or other rights that might be claimed to
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Copyright Statement

   Copyright (C) The Internet Society (2005).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




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