Network Working Group J. F. Reschke Internet Draft greenbytes Expires: September 2002 March 2002 Computing the CHECKIN URI in WebDAV versioning draft-reschke-deltav-compute-checkin-uri-01 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire in September 2002. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract In many cases, a versioning-aware client might want to display/include the URI of the version it's editing while it's being edited. For instance, an editor might include this as meta information, or the author of a document might want to know the URI of the version before it's checked in. A well-known example is the W3C way of referring to document versions in recommendations: it contains references to "the current version", to "this version" and to the "previous version". Something like this is currently impossible with WebDAV deltaV [RFC3253], as the version URI is Reschke Expires September 2002 [Page 1] Internet Draft CHECKIN URI in WebDAV versioning March 2002 determined at the time of CHECKIN. Distribution of this document is unlimited. Please send comments to the WebDAV versioning (delta-V) working group at ietf-dav- versioning@w3.org, which may be joined by sending a message with subject "subscribe" to ietf-dav-versioning-request@w3.org. Discussions of the delta-V working group are archived at URL: http://lists.w3.org/Archives/Public/ietf-dav-versioning/. Reschke Expires September 2002 [Page 2] Internet Draft CHECKIN URI in WebDAV versioning March 2002 Table of Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . 3 1 Notational Conventions . . . . . . . . . . . . . . . . . . . . 4 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Changes for CHECKOUT method (when applied to a version- controlled resource) . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Example for successful CHECKOUT with computed version URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Example for successful CHECKOUT without computed version URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 Changes for CHECKIN method (when applied to a version- controlled resource) . . . . . . . . . . . . . . . . . . . . . . 9 4.1 Example for successful CHECKIN with computed version URI . 9 4.2 Example for failed CHECKIN with computed version URI . . . 10 5 Compatibility Considerations . . . . . . . . . . . . . . . . . 11 6 Internationalization Considerations . . . . . . . . . . . . . . 12 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 13 8 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9 Intellectual Property . . . . . . . . . . . . . . . . . . . . . 15 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 A Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 17 A.1 Since 'draft-reschke-deltav-compute-checkin-uri-00' . . . . 17 Reschke Expires September 2002 [Page 3] Internet Draft CHECKIN URI in WebDAV versioning March 2002 1 Notational Conventions 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]. Reschke Expires September 2002 [Page 4] Internet Draft CHECKIN URI in WebDAV versioning March 2002 2 Introduction In many cases, a versioning-aware client might want to display/include the URI of the version it's editing while it's being edited. For instance, an editor might include this as meta information, or the author of a document might want to know the URI of the version before it's checked in. A well-known example is the W3C way of referring to document versions in recommendations: it contains references to "the current version", to "this version" and to the "previous version". Something like this is currently impossible with WebDAV deltaV [RFC3253], as the version URI is determined at the time of CHECKIN. This specification builds on the infrastructure provided by the WebDAV Versioning Protocol, adding support for servers willing to compute an "expected version URI" upon CHECKOUT, and using this URI at time of CHECKIN. This document defines an extension element that could ultimately become part of the WebDAV deltaV protocol. Being just an individual submission, it currently defines it in the proprietary namespace http://sapportals.com/xmlns/cm/webdav instead of the "DAV:" namespace. It uses a prefix of "cu:" for referring to elements in this namespace. However, WebDAV server and clients are free to use any prefix, provided that there is a namespace declaration that binds the prefix to the URI of the same namespace. Reschke Expires September 2002 [Page 5] Internet Draft CHECKIN URI in WebDAV versioning March 2002 3 Changes for CHECKOUT method (when applied to a version-controlled resource) A client may ask for an "expected version URI" upon CHECKOUT. This is done by placing cu:compute-expected-version-URI as top-level element into the request body. The server is free to either ignore the request, or to return it's best guess about what the URI for a version resource created upon CHECKIN would be. The client can detect the "expected version URI" by parsing the response body for a top-level element called cu:expected-version-URI. 3.1 Example for successful CHECKOUT with computed version URI >>Request CHECKOUT /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx >>Response HTTP/1.1 200 OK Cache-Control: no-cache Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.webdav.org/his/23/ver/32 Reschke Expires September 2002 [Page 6] Internet Draft CHECKIN URI in WebDAV versioning March 2002 In this example, the server was able to compute the "expected version URI" and returned it in the cu:expected-version-URI element. 3.2 Example for successful CHECKOUT without computed version URI >>Request CHECKOUT /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx >>Response HTTP/1.1 200 OK Cache-Control: no-cache In this case, no response body was returned, and thus no "expected version URI" is available. Simarily, the server may also return >>Response HTTP/1.1 200 OK Cache-Control: no-cache Content-Type: text/xml; charset="utf-8" Content-Length: xxxx ...other content... Reschke Expires September 2002 [Page 7] Internet Draft CHECKIN URI in WebDAV versioning March 2002 where a response body is available, but it doesn't contain the cu:expected-version-URI element. Reschke Expires September 2002 [Page 8] Internet Draft CHECKIN URI in WebDAV versioning March 2002 4 Changes for CHECKIN method (when applied to a version-controlled resource) A client may submit the "expected version URI" (obtained during CHECKOUT) upon a CHECKIN by placing it into a top-level cu:expected- version-URI element in the request body. A server may o simply ignore the presence of this information or o use the information and try to checkin the resource using the "expected version URI" as location for the version resource. A failure to create a version resource at the "expected version URI" MUST cause the operation to fail with a status code of 403 (forbidden) and a response body containing the top-level element cu:cannot-assign-expected-version-URI. In addition, a server MAY return a new "expected version URI" in it's response body. 4.1 Example for successful CHECKIN with computed version URI >>Request CHECKIN /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.webdav.org/his/23/ver/32 >>Response HTTP/1.1 201 Created Location: http://repo.webdav.org/his/23/ver/32 Cache-Control: no-cache Note that the client can not rely on the server signaling an error if the expected version URI could not be applied. It will have to Reschke Expires September 2002 [Page 9] Internet Draft CHECKIN URI in WebDAV versioning March 2002 compare the URI returned in the HTTP "Location" header with the requested version URI, and in the case of mismatch it MAY have to report the situation to the user. 4.2 Example for failed CHECKIN with computed version URI >>Request CHECKIN /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.webdav.org/his/23/ver/32 >>Response HTTP/1.1 403 Forbidden Cache-Control: no-cache Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.webdav.org/his/23/ver/33 Reschke Expires September 2002 [Page 10] Internet Draft CHECKIN URI in WebDAV versioning March 2002 5 Compatibility Considerations This specification does introduce new protocol elements for the request and response bodies for CHECKIN and CHECKOUT. Clients not aware of this specification will never submit the new protocol elements in a request and therefore never will see the new response elements. Servers not aware of this specification will ignore the additional two request body elements which is legal behaviour according to this protocol (indicating that the protocol extension is not available). Reschke Expires September 2002 [Page 11] Internet Draft CHECKIN URI in WebDAV versioning March 2002 6 Internationalization Considerations This proposal builds on [RFC3253], and inherits its internationalizability. Reschke Expires September 2002 [Page 12] Internet Draft CHECKIN URI in WebDAV versioning March 2002 7 IANA Considerations This proposal does not introduce any new IANA considerations, since it does not specify any new namespaces (in the general sense), but merely uses existing ones. Reschke Expires September 2002 [Page 13] Internet Draft CHECKIN URI in WebDAV versioning March 2002 8 Copyright To be supplied by the RFC Editor. Reschke Expires September 2002 [Page 14] Internet Draft CHECKIN URI in WebDAV versioning March 2002 9 Intellectual Property To be supplied by the RFC Editor. Reschke Expires September 2002 [Page 15] Internet Draft CHECKIN URI in WebDAV versioning March 2002 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.R. and Jensen, D., "HTTP Extensions for Distributed Authoring -- WEBDAV", RFC 2518, February 1999. [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and Whitehead, J., "Versioning Extensions to WebDAV", RFC 3253, March 2002. 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://www.greenbytes.de/tech/webdav/ Reschke Expires September 2002 [Page 16] Internet Draft CHECKIN URI in WebDAV versioning March 2002 A Change Log A.1 Since 'draft-reschke-deltav-compute-checkin-uri-00' Made the document element for responses upon failed CHECKIN DAV:error rather than DAV:checkin-response. Updated reference to [RFC3253]. Moved extension elements out of DAV: namespace. Changed examples to explicitly use utf-8 encoding for HTTP content type and XML encoding. Globally replaced the term "CHECKIN URI" by "version URI" Added note about how to discover whether the server actually applied the expected version URI. Made sure artwork (figures) fits into 72 columns. Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Reschke Expires September 2002 [Page 17] Internet Draft CHECKIN URI in WebDAV versioning March 2002 Acknowledgement Funding for the RFC editor function is currently provided by the Internet Society. Reschke Expires September 2002 [Page 18]