Network Working Group J. Reschke Internet-Draft greenbytes Expires: February 18, 2004 August 20, 2003 Computing the CHECKIN URI in WebDAV versioning draft-reschke-deltav-compute-checkin-uri-05 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 on February 18, 2004. Copyright Notice Copyright (C) The Internet Society (2003). 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 versioning [RFC3253], as the version URI is determined at the time of CHECKIN. Distribution of this document is unlimited. Please send comments to the WebDAV versioning (delta-V) mailing list at Reschke Expires February 18, 2004 [Page 1] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 ietf-dav-versioning@w3.org [1], which may be joined by sending a message with subject "subscribe" to ietf-dav-versioning-request@w3.org [2]. Discussions of the delta-V mailing list are archived at URL: http://lists.w3.org/Archives/ Public/ietf-dav-versioning/. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4 3. Changes for CHECKOUT method . . . . . . . . . . . . . . . . . 5 3.1 Example for successful CHECKOUT with computed version URI . . 5 3.2 Example for successful CHECKOUT without computed version URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Changes for CHECKIN method (when applied to a version-controlled resource) . . . . . . . . . . . . . . . . . 8 4.1 Example for successful CHECKIN with computed version URI . . . 8 4.2 Example for failed CHECKIN with computed version URI . . . . . 9 5. Compatibility Considerations . . . . . . . . . . . . . . . . . 10 6. Internationalization Considerations . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 13 A. Change Log (to be removed by RFC Editor before publication) . 14 A.1 Since 'draft-reschke-deltav-compute-checkin-uri-00' . . . . . 14 A.2 Since 'draft-reschke-deltav-compute-checkin-uri-01' . . . . . 14 A.3 Since 'draft-reschke-deltav-compute-checkin-uri-02' . . . . . 14 A.4 Since 'draft-reschke-deltav-compute-checkin-uri-03' . . . . . 14 A.5 Since 'draft-reschke-deltav-compute-checkin-uri-04' . . . . . 14 B. Resolved issues (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . . . . . . 15 B.1 required-checkin-behaviour . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . 16 Reschke Expires February 18, 2004 [Page 2] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 1. 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 versioning [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 versioning 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 February 18, 2004 [Page 3] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 2. 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 February 18, 2004 [Page 4] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 3. Changes for CHECKOUT method A client may ask for an "expected version URI" upon CHECKOUT (and the CHECKIN variant with DAV:keep-checked-out request element). This is done by placing cu:compute-expected-version-URI as top-level element into the request body. Additional Marshalling: Presence of the cu:compute-expected-version-URI as top-level element in the request body indicates that the server SHOULD compute the "expected version URI". 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. Absence of this element (or absence of a response body) indicates that the server is not able to compute the URI. 3.1 Example for successful CHECKOUT with computed version URI >>Request CHECKOUT /foo.html HTTP/1.1 Host: www.example.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx >>Response HTTP/1.1 200 OK Reschke Expires February 18, 2004 [Page 5] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 Cache-Control: no-cache Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.example.org/his/23/ver/32 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.example.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 February 18, 2004 [Page 6] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 where a response body is available, but it doesn't contain the cu:expected-version-URI element. Reschke Expires February 18, 2004 [Page 7] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 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. Additional Marshalling: A top-level element cu:expected-version-URI, when present, indicates the client's expectation about the URI of the version that will be created by the CHECKIN operation. Upon failure, the server MAY return a new "expected version URI" in the DAV:error response body using the element cu:expected-version-URI. Additional Preconditions: (cu:can-assign-expected-version-URI): if the server does support the cu:compute-expected-version-URI extension upon CHECKOUT, it MUST create the new version at the URI specified in the cu:expected-version-URI or otherwise fail the request. 4.1 Example for successful CHECKIN with computed version URI >>Request CHECKIN /foo.html HTTP/1.1 Host: www.example.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.example.org/his/23/ver/32 >>Response HTTP/1.1 201 Created Location: http://repo.example.org/his/23/ver/32 Cache-Control: no-cache Reschke Expires February 18, 2004 [Page 8] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 4.2 Example for failed CHECKIN with computed version URI >>Request CHECKIN /foo.html HTTP/1.1 Host: www.example.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx http://repo.example.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.example.org/his/23/ver/33 Note that 403 (Forbidden) is returned because subsequent request with the same expected version URI will always fail. Reschke Expires February 18, 2004 [Page 9] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 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 February 18, 2004 [Page 10] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 6. Internationalization Considerations This proposal builds on [RFC3253], and inherits its internationalizability. Reschke Expires February 18, 2004 [Page 11] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 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 February 18, 2004 [Page 12] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 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. [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and J. Whitehead, "Versioning Extensions to WebDAV", RFC 3253, March 2002. [1] [2] 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/ Reschke Expires February 18, 2004 [Page 13] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 Appendix A. Change Log (to be removed by RFC Editor before publication) 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. A.2 Since 'draft-reschke-deltav-compute-checkin-uri-01' Updated abstract not to refer to DeltaV WG anymore. Use "WebDAV versioning" instead of "deltaV". Changed descriptions to use RFC3253's Marshalling/Precondition format. Changed name of cu:cannot-assign-expected-version-URI to cu:can-assign-expected-version-URI as this is a precondition. A.3 Since 'draft-reschke-deltav-compute-checkin-uri-02' Update marshalling to use DAV:href as container for URIs. Clarify that the extension applies to CHECKOUT on version resources and to CHECKIN/DAV:keep-checked-out as well. A.4 Since 'draft-reschke-deltav-compute-checkin-uri-03' Replaced domain names in examples according to RFC2606: "webdav.org" by "example.org". A.5 Since 'draft-reschke-deltav-compute-checkin-uri-04' Remove superfluous IP and copyright sections. Swap "Introduction" and "Notation" sections. Require server to support both extensions to make behaviour more predictable. Reschke Expires February 18, 2004 [Page 14] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 Appendix B. Resolved issues (to be removed by RFC Editor before publication) Issues that were either rejected or resolved in this version of this document. B.1 required-checkin-behaviour Type: change julian.reschke@greebytes.de (2003-08-20): The CHECKIN extension is of little value if the client can not detect beforehand whether it will be respected. Resolution: Require support for CHECKIN extension if the server does support the CHECKOUT extension. Reschke Expires February 18, 2004 [Page 15] Internet-Draft CHECKIN URI in WebDAV versioning August 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. 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