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Network Working Group J. Slein Request for Comments: 2291 Xerox Corporation Category: Informational F. Vitali

                                                University of Bologna
                                                         E. Whitehead
                                                          U.C. Irvine
                                                            D. Durand
                                                    Boston University
                                                        February 1998
      Requirements for a Distributed Authoring and Versioning
                  Protocol for the World Wide Web

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1998).  All Rights Reserved.


 Current World Wide Web (WWW or Web) standards provide simple support
 for applications which allow remote editing of typed data. In
 practice, the existing capabilities of the WWW have proven inadequate
 to support efficient, scalable remote editing free of overwriting
 conflicts. This document presents a list of features in the form of
 requirements for a Web Distributed Authoring and Versioning protocol
 which, if implemented, would improve the efficiency of common remote
 editing operations, provide a locking mechanism to prevent overwrite
 conflicts, improve link management support between non-HTML data
 types, provide a simple attribute-value metadata facility, provide
 for the creation and reading of container data types, and integrate
 versioning into the WWW.

1. Introduction

 This document describes functionality which, if incorporated in an
 extension to the existing HTTP proposed standard [HTTP], would allow
 tools for remote loading, editing and saving (publishing) of various
 media types on the WWW to interoperate with any compliant Web server.
 As much as possible, this functionality is described without
 suggesting a proposed implementation, since there are many ways to
 perform the functionality within the WWW framework. It is also

Slein, et. al. Informational [Page 1] RFC 2291 Distributed Authoring and Versioning February 1998

 possible that a single mechanism could simultaneously satisfy several
 This document reflects the consensus of the WWW Distributed Authoring
 and Versioning working group (WebDAV) as to the functionality that
 should be standardized to support distributed authoring and
 versioning on the Web.  As with any set of requirements, practical
 considerations may make it impossible to satisfy them all.  It is the
 intention of the WebDAV working group to come as close as possible to
 satisfying them in the specifications that make up the WebDAV

2. Rationale

 Current Web standards contain functionality which enables the editing
 of Web content at a remote location, without direct access to the
 storage media via an operating system. This capability is exploited
 by several existing HTML distributed authoring tools, and by a
 growing number of mainstream applications (e.g., word processors)
 which allow users to write (publish) their work to an HTTP server. To
 date, experience from the HTML authoring tools has shown they are
 unable to meet their users' needs using the facilities of Web
 standards. The consequence of this is either postponed introduction
 of distributed authoring capability, or the addition of nonstandard
 extensions to the HTTP protocol or other Web standards.  These
 extensions, developed in isolation, are not interoperable.
 Other authoring applications have wanted to access document
 repositories or version control systems through Web gateways, and
 have been similarly frustrated.  Where this access is available at
 all, it is through nonstandard extensions to HTTP or other standards
 that force clients to use a different interface for each vendor's
 This document describes requirements for a set of standard extensions
 to HTTP that would allow distributed Web authoring tools to provide
 the functionality their users need by means of the same standard
 syntax across all compliant servers. The broad categories of
 functionality that need to be standardized are:
      Retrieval of Unprocessed Source
      Partial Write
      Name Space Manipulation

Slein, et. al. Informational [Page 2] RFC 2291 Distributed Authoring and Versioning February 1998


3. Terminology

 Where there is overlap, usage is intended to be consistent with that
 in the HTTP 1.1 specification [HTTP].
      A program which issues HTTP requests and accepts responses.
      A collection is a resource that contains other resources, either
      directly or by reference.
 Distributed Authoring Tool
      A program which can retrieve a source entity via HTTP, allow
      editing of this entity, and then save/publish this entity to a
      server using HTTP.
      The information transferred in a request or response.
 Hierarchical Collection
      A hierarchical organization of resources.  A hierarchical
      collection is a resource that contains other resources,
      including collections, either directly or by reference.
      A typed connection between two or more resources.
      A mechanism for preventing anyone other than the owner of the
      lock from accessing a resource.
 Member of Version Graph
      A resource that is a node in a version graph, and so is derived
      from the resources that precede it in the graph, and is the
      basis of those that succeed it.
      Named descriptive information about a resource.
      A declaration that one intends to edit a resource.

Slein, et. al. Informational [Page 3] RFC 2291 Distributed Authoring and Versioning February 1998

      A network data object or service that can be identified by a
      A program which receives and responds to HTTP requests.
 User Agent
      The client that initiates a request.
      A representation of a resource.  A resource may have one or more
      representations associated with it at any given time.
 Version Graph
      A directed acyclic graph with resources as its nodes, where each
      node is derived from its predecessor(s).
 Write Lock
      A lock that prevents anyone except its owner from modifying the
      resource it applies to.

4. General Principles

 This section describes a set of general principles that the WebDAV
 extensions should follow.  These principles cut across categories of

4.1. User Agent Interoperability

 All WebDAV clients should be able to work with any WebDAV-compliant
 HTTP server. It is acceptable for some client/server combinations to
 provide special features that are not universally available, but the
 protocol should be sufficient that a basic level of functionality
 will be universal.

4.2. Client Simplicity

 The WebDAV extensions should be designed to allow client
 implementations to be simple.

Slein, et. al. Informational [Page 4] RFC 2291 Distributed Authoring and Versioning February 1998

4.3. Legacy Client Support

 It should be possible to implement a WebDAV-compliant server in such
 a way that it can interoperate with non-WebDAV clients.  Such a
 server would be able to understand any valid HTTP 1.1 request from an
 ordinary Web client without WebDAV extensions, and to provide a valid
 HTTP 1.1 response that does not require the client to understand the

4.4. Data Format Compatibility

 WebDAV-compliant servers should be able to work with existing
 resources and URIs [URL]. Special additional information should not
 become a mandatory part of document formats.

4.5. Replicated, Distributed Systems

 Distribution and replication are at the heart of the Internet.  All
 WebDAV extensions should be designed to allow for distribution and
 replication.  Version trees should be able to be split across
 multiple servers.  Collections may have members on different servers.
 Any resource may be cached or replicated for mobile computing or
 other reasons.  Consequently, the WebDAV extensions must be able to
 operate in a distributed, replicated environment.

4.6 Parsimony in Client-Server Interactions

 The WebDAV extensions should keep to a minimum the number of
 interactions between the client and the server needed to perform
 common functions. For example, publishing a document to the Web will
 often mean publishing content together with related properties.  A
 client may often need to find out what version graph a particular
 resource belongs to, or to find out which resource in a version graph
 is the published one.  The extensions should make it possible to do
 these things efficiently.

4.7. Changes to HTTP

 WebDAV adds a number of new types of objects to the Web: properties,
 collections, version graphs, etc.  Existing HTTP methods such as
 DELETE and PUT will have to operate in well-defined ways in this
 expanded environment. WebDAV should explicitly address not only new
 methods, headers, and MIME types, but also any required changes to
 the existing HTTP methods and headers.

Slein, et. al. Informational [Page 5] RFC 2291 Distributed Authoring and Versioning February 1998

4.8. Alternate Transport Mechanisms

 It may be desirable to transport WebDAV requests and responses by
 other mechanisms, particularly EMail, in addition to HTTP.  The
 WebDAV protocol specification should not preclude a future body from
 developing an interoperability specification for disconnected
 operation via EMail.

5. Requirements

 In the requirement descriptions below, the requirement will be
 stated, followed by its rationale.

5.1. Properties

5.1.1. Functional Requirements

 It must be possible to create, modify, read and delete arbitrary
 properties on resources of any media type.

5.1.2. Rationale

 Properties describe resources of any media type.  They may include
 bibliographic information such as author, title, publisher, and
 subject, constraints on usage, PICS ratings, etc. These properties
 have many uses, such as supporting searches on property values,
 enforcing copyrights, and the creation of catalog entries as
 placeholders for objects which are not available in electronic form,
 or which will be available later.

5.2. Links

5.2.1. Functional Requirements

 It must be possible to create, modify, read and delete typed links
 between resources of any media type.

5.2.2. Rationale

 One type of link between resources is the hypertext link, which is
 browsable using a hypertext style point-and-click user interface.
 Links, whether they are browsable hypertext links, or simply a means
 of capturing a relationship between resources, have many purposes.
 Links can support pushbutton printing of a multi-resource document in
 a prescribed order, jumping to the access control page for a
 resource, and quick browsing of related information, such as a table

Slein, et. al. Informational [Page 6] RFC 2291 Distributed Authoring and Versioning February 1998

 of contents, an index, a glossary, a bibliographic record, help
 pages, etc. While link support is provided by the HTML "LINK"
 element, this is limited only to HTML resources [HTML]. Similar
 support is needed for bitmap image types, and other non-HTML media

5.3. Locking

5.3.1. General Principles Independence of locks. It must be possible to lock a
 resource without performing an additional retrieval of the resource,
 and without committing to editing the resource. Multi-Resource Locking. It must be possible to take out a
 lock on multiple resources residing on the same server in a single
 action, and this locking operation must be atomic across these

5.3.2. Functional Requirements Write Locks. It must be possible to restrict modification of
 a resource to a specific person. Lock Query. It must be possible to find out whether a given
 resource has any active locks, and if so, who holds those locks. Unlock. It must be possible to remove a lock.

5.3.3. Rationale

 At present, the Web provides limited support for preventing two or
 more people from overwriting each other's modifications when they
 save to a given URI. Furthermore, there is no way to discover whether
 someone else is currently making modifications to a resource. This is
 known as the "lost update problem," or the "overwrite problem." Since
 there can be significant cost associated with discovering and
 repairing lost modifications, preventing this problem is crucial for
 supporting distributed authoring. A write lock ensures that only one
 person may modify a resource, preventing overwrites. Furthermore,
 locking support is a key component of many versioning schemes, a
 desirable capability for distributed authoring.
 An author may wish to lock an entire web of resources even though he
 is editing just a single resource, to keep the other resources from
 changing. In this way, an author can ensure that if a local hypertext
 web is consistent in his distributed authoring tool, it will then be

Slein, et. al. Informational [Page 7] RFC 2291 Distributed Authoring and Versioning February 1998

 consistent when he writes it to the server. Because of this, it
 should be possible to take out a lock without also causing
 transmission of the contents of a resource.
 It is often necessary to guarantee that a lock or unlock operation
 occurs at the same time across multiple resources, a feature which is
 supported by the multiple-resource locking requirement. This is
 useful for preventing a collision between two people trying to
 establish locks on the same set of resources, since with multi-
 resource locking, one of the two people will get a lock. If this same
 multiple-resource locking scenario was repeated by using atomic lock
 operations iterated across the resources, the result would be a
 splitting of the locks between the two people, based on resource
 ordering and race conditions.

5.4. Reservations

5.4.1. Functional Requirements Reserve. It must be possible for a principal to register
 with the server an intent to edit a given resource, so that other
 principals can discover who intends to edit the resource. Reservation Query. It must be possible to find out whether a
 given resource has any active reservations, and if so, who currently
 holds reservations. Release Reservation.  It must be possible to release the

5.4.2. Rationale

 Experience from configuration management systems has shown that
 people need to know when they are about to enter a parallel editing
 situation. Once notified, they either decide not to edit in parallel
 with the other authors, or they use out-of-band communication (face-
 to-face, telephone, etc.) to coordinate their editing to minimize the
 difficulty of merging their results. Reservations are separate from
 locking, since a write lock does not necessarily imply a resource
 will be edited, and a reservation does not carry with it any access
 restrictions. This capability supports versioning, since a check-out
 typically involves taking out a write lock, making a reservation, and
 getting the resource to be edited.

Slein, et. al. Informational [Page 8] RFC 2291 Distributed Authoring and Versioning February 1998

5.5. Retrieval of Unprocessed Source for Editing

5.5.1. Functional Requirement

 The source of any given resource must be retrievable by any principal
 with authorization to edit the resource.

5.5.2. Rationale

 There are many cases where the source stored on a server does not
 correspond to the actual entity transmitted in response to an HTTP
 GET. Current known cases are server side include directives, and
 Standard Generalized Markup Language (SGML) source which is converted
 on the fly to HyperText Markup Language (HTML) [HTML] output
 entities. There are many possible cases, such as automatic conversion
 of bitmap images into several variant bitmap media types (e.g. GIF,
 JPEG), and automatic conversion of an application's native media type
 into HTML. As an example of this last case, a word processor could
 store its native media type on a server which automatically converts
 it to HTML. A GET of this resource would retrieve the HTML.
 Retrieving the source would retrieve the word processor native

5.6. Partial Write.

5.6.1. Functional Requirement

 After editing a resource, it must be possible to write only the
 changes to the resource, rather than retransmitting the entire

5.6.2. Rationale

 During distributed editing which occurs over wide geographic
 separations and/or over low bandwidth connections, it is extremely
 inefficient and frustrating to rewrite a large resource after minor
 changes, such as a one-character spelling correction. Support is
 needed for transmitting "insert" (e.g., add this sentence in the
 middle of a document) and "delete" (e.g. remove this paragraph from
 the middle of a document) style updates. Support for partial resource
 updates will make small edits more efficient, and allow distributed
 authoring tools to scale up for editing large documents.

Slein, et. al. Informational [Page 9] RFC 2291 Distributed Authoring and Versioning February 1998

5.7. Name Space Manipulation

5.7.1. Copy Functional Requirements

 It must be possible to duplicate a resource without a client loading,
 then resaving the resource. After the copy operation, a modification
 to either resource must not cause a modification to the other. Rationale

 There are many reasons why a resource might need to be duplicated,
 such as changing ownership, preparing for major modifications, or
 making a backup. Due to network costs associated with loading and
 saving a resource, it is far preferable to have a server perform a
 resource copy than a client.

5.7.2. Move/Rename Functional Requirements

 It must be possible to change the location of a resource without a
 client loading, then resaving the resource under a different name.
 After the move operation, it must no longer be possible to access the
 resource at its original location. Rationale

 It is often necessary to change the name of a resource, for example
 due to adoption of a new naming convention, or if a typing error was
 made entering the name originally. Due to network costs, it is
 undesirable to perform this operation by loading, then resaving the
 resource, followed by a delete of the old resource. Similarly, a
 single rename operation is more efficient than a copy followed by a
 delete operation.  Note that moving a resource is considered the same
 function as renaming a resource.

5.8. Collections

 A collection is a resource that is a container for other resources,
 including other collections.  A resource may belong to a collection
 either directly or by reference.  If a resource belongs to a
 collection directly, name space operations like copy, move, and
 delete applied to the collection also apply to the resource.  If a
 resource belongs to a collection by reference, name space operations
 applied to the collection affect only the reference, not the resource

Slein, et. al. Informational [Page 10] RFC 2291 Distributed Authoring and Versioning February 1998

5.8.1. Functional Requirements List Collection. A listing of all resources in a specific
 collection must be accessible. Make Collection. It must be possible to create a new
 collection. Add to Collection.  It must be possible to add a resource to
 a collection directly or by reference. Remove from Collection.  It must be possible to remove a
 resource from a collection.

5.8.2. Rationale

 In [URL] it states that, "some URL schemes (such as the ftp, http,
 and file schemes) contain names that can be considered hierarchical."
 Especially for HTTP servers which directly map all or part of their
 URL name space into a filesystem, it is very useful to get a listing
 of all resources located at a particular hierarchy level. This
 functionality supports "Save As..." dialog boxes, which provide a
 listing of the entities at a current hierarchy level, and allow
 navigation through the hierarchy. It also supports the creation of
 graphical visualizations (typically as a network) of the hypertext
 structure among the entities at a hierarchy level, or set of levels.
 It also supports a tree visualization of the entities and their
 hierarchy levels.
 In addition, document management systems may want to make their
 documents accessible through the Web.  They typically allow the
 organization of documents into collections, and so also want their
 users to be able to view the collection hierarchy through the Web.
 There are many instances where there is not a strong correlation
 between a URL hierarchy level and the notion of a collection. One
 example is a server in which the URL hierarchy level maps to a
 computational process which performs some resolution on the name. In
 this case, the contents of the URL hierarchy level can vary depending
 on the input to the computation, and the number of resources
 accessible via the computation can be very large. It does not make
 sense to implement a directory feature for such a name space.
 However, the utility of listing the contents of those URL hierarchy
 levels which do correspond to collections, such as the large number
 of HTTP servers which map their name space to a filesystem, argue for
 the inclusion of this capability, despite not being meaningful in all

Slein, et. al. Informational [Page 11] RFC 2291 Distributed Authoring and Versioning February 1998

 cases. If listing the contents of a URL hierarchy level does not
 makes sense for a particular URL, then a "405 Method Not Allowed"
 status code could be issued.
 The ability to create collections to hold related resources supports
 management of a name space by packaging its members into small,
 related clusters. The utility of this capability is demonstrated by
 the broad implementation of directories in recent operating systems.
 The ability to create a collection also supports the creation of
 "Save As..." dialog boxes with "New Level/Folder/Directory"
 capability, common in many applications.

5.9. Versioning

5.9.1. Background and General Principles Stability of versions. Most versioning systems are intended
 to provide an accurate record of the history of evolution of a
 document. This accuracy is ensured by the fact that a version
 eventually becomes "frozen" and immutable. Once a version is frozen,
 further changes will create new versions rather than modifying the
 original. In order for caching and persistent references to be
 properly maintained, a client must be able to determine that a
 version has been frozen. Any successful attempt to retrieve a frozen
 version of a resource will always retrieve exactly the same content,
 or return an error if that version (or the resource itself) is no
 longer available. Operations for Creating New Versions.  Version management
 systems vary greatly in the operations they require, the order of the
 operations, and how they are combined into atomic functions.  In the
 most complete cases, the logical operations involved are:
      o Reserve existing version
      o Lock existing version
      o Retrieve existing version
      o Request or suggest identifier for new version
      o Write new version
      o Release lock
      o Release reservation
 With the exception of requesting a new version identifier, all of
 these operations have applications outside of versioning and are
 either already part of HTTP or are discussed in earlier sections of
 these requirements. Typically, versioning systems combine
 reservation, locking, and retrieval -- or some subset of these --
 into an atomic checkout function.  They combine writing, releasing

Slein, et. al. Informational [Page 12] RFC 2291 Distributed Authoring and Versioning February 1998

 the lock, and releasing the reservation -- or some subset of these --
 into an atomic checkin function.  The new version identifier may be
 assigned either at checkout or at checkin.
 The WebDAV extensions must find some balance between allowing
 versioning servers to adopt whatever policies they wish with regard
 to these operations and enforcing enough uniformity to keep client
 implementations simple. The Versioning Model.  Each version typically stands in a
 "derived from" relationship to its predecessor(s).  It is possible to
 derive several different versions from a single version (branching),
 and to derive a single version from several versions (merging).
 Consequently, the collection of related versions forms a directed
 acyclic graph.  In the following discussion, this graph will be
 called a "version graph".  Each node of this graph is a "version" or
 "member of the version graph".  The arcs of the graph capture the
 "derived from" relationships.
 It is also possible for a single resource to participate in multiple
 version graphs.
 The WebDAV extensions should support this versioning model, though
 particular servers may restrict it in various ways. Versioning Policies. Many writers, including Feiler [CM] and
 Haake and Hicks [VSE], have discussed the notion of versioning styles
 (referred to here as versioning policies, to reflect the nature of
 client/server interaction) as one way to think about the different
 policies that versioning systems implement. Versioning policies
 include decisions on the shape of version histories (linear or
 branched), the granularity of change tracking, locking requirements
 made by a server, etc. The protocol should clearly identify the
 policies that it dictates and the policies that are left up to
 versioning system implementors or administrators. It is possible to version resources of any media type.

5.9.2. Functional Requirements Referring to a version graph. There must be a way to refer
 to a version graph as a whole.
 Some queries and operations apply, not to any one member of a version
 graph, but to the version graph as a whole.  For example, a client
 may request that an entire graph be moved, or may ask for a version
 history. In these cases, a way to refer to the whole version graph is

Slein, et. al. Informational [Page 13] RFC 2291 Distributed Authoring and Versioning February 1998 Referring to a specific member of a version graph. There
 must be a way to refer to each member of a version graph. This means
 that each member of the graph is itself a resource.
 Each member of a version graph must be a resource if it is to be
 possible for a hypertext link to refer to specific version of a page,
 or for a client to request a specific version of a document for
 editing. A client must be able to determine whether a resource is a
 version graph, or whether a resource is itself a member of a version
 A resource may be a simple, non-versioned resource, or it may be a
 version graph, or it may be a member of a version graph.  A client
 needs to be able to tell which sort of resource it is accessing. There must be a way to refer to a server-defined default
 member of a version graph.
 The server should return a default version of a resource for requests
 that ask for the default version, as well as for requests where no
 specific version information is provided. This is one of the simplest
 ways to guarantee non-versioning client compatibility. This does not
 rule out the possibility of a server returning an error when no
 sensible default exists.
 It may also be desirable to be able to refer to other special members
 of a version graph. For example, there may be a current version for
 editing that is different from the default version.  For a graph with
 several branches, it may be useful to be able to request the tip
 version of any branch. It must be possible, given a reference to a member of a
 version graph, to find out which version graph(s) that resource
 belongs to.
 This makes it possible to understand the versioning context of the
 resource. It makes it possible to retrieve a version history for the
 graphs to which it belongs, and to browse the version graph. It also
 supports some comparison operations: It makes it possible to
 determine whether two references designate members of the same
 version graph. Navigation of a version graph.  Given a reference to a
 member of a version graph, it must be possible to discover and access
 the following related members of the version graph.

Slein, et. al. Informational [Page 14] RFC 2291 Distributed Authoring and Versioning February 1998

      o root member of the graph
      o predecessor member(s)
      o successor member(s)
      o default member of the graph
 It must be possible in some way for a versioning client to access
 versions related to a resource currently being examined. Version Topology. There must be a way to retrieve the
 complete version topology for a version graph, including information
 about all members of the version graph. The format for this
 information must be standardized so that the basic information can be
 used by all clients. Other specialized formats should be
 accommodated, for servers and clients that require information that
 cannot be included in the standard topology. A client must be able to propose a version identifier to be
 used for a new member of a version graph. The server may refuse to
 use the client's suggested version identifier.  The server should
 tell the client what version identifier it has assigned to the new
 member of the version graph. A version identifier must be unique across a version graph. A client must be able to supply version-specific properties
 to be associated with a new member of a version graph. (See Section
 5.1 "Properties" above.) At a minimum, it must be possible to
 associate comments with the new member, explaining what changes were
 made. A client must be able to query the server for information
 about a version tree, including which versions are locked, which are
 reserved for editing, and by whom (Session Tracking).

5.9.3. Rationale

 Versioning in the context of the world-wide web offers a variety of
 It provides infrastructure for efficient and controlled management of
 large evolving web sites. Modern configuration management systems are
 built on some form of repository that can track the revision history
 of individual resources, and provide the higher-level tools to manage
 those saved versions. Basic versioning capabilities are required to
 support such systems.

Slein, et. al. Informational [Page 15] RFC 2291 Distributed Authoring and Versioning February 1998

 It allows parallel development and update of single resources. Since
 versioning systems register change by creating new objects, they
 enable simultaneous write access by allowing the creation of variant
 versions. Many also provide merge support to ease the reverse
 It provides a framework for coordinating changes to resources. While
 specifics vary, most systems provide some method of controlling or
 tracking access to enable collaborative resource development.
 It allows browsing through past and alternative versions of a
 resource.  Frequently the modification and authorship history of a
 resource is critical information in itself.
 It provides stable names that can support externally stored links for
 annotation and link-server support. Both annotation and link servers
 frequently need to store stable references to portions of resources
 that are not under their direct control. By providing stable states
 of resources, version control systems allow not only stable pointers
 into those resources, but also well-defined methods to determine the
 relationships of those states of a resource.
 It allows explicit semantic representation of single resources with
 multiple states. A versioning system directly represents the fact
 that a resource has an explicit history, and a persistent identity
 across the various states it has had during the course of that

5.10. Variants

 Detailed requirements for variants will be developed in a separate

5.10.1. Functional Requirements

 It must be possible to send variants to the server, describing the
 relationships between the variants and their parent resource.  In
 addition, it must be possible to write and retrieve variants of
 property labels, property descriptions, and property values.

5.10.2. Rationale

 The HTTP working group is addressing problems of content negotiation
 and retrieval of variants of a resource.  To extend this work to an
 authoring environment, WEBDAV must standardize mechanisms for authors
 to use when submitting variants to a server.  Authors need to be able
 to provide variants in different file or document formats, for
 different uses. They need to provide variants optimized for different

Slein, et. al. Informational [Page 16] RFC 2291 Distributed Authoring and Versioning February 1998

 clients and for different output devices.  They need to be able to
 provide variants in different languages in the international
 environment of the Web.  In support of internationalization
 requirements (See 5.12 below), variants need to be supported not just
 for the content of resources, but for any information intended for
 human use, such as property values, labels, and descriptions.

5.11. Security

 5.11.1. Authentication. The WebDAV specification should state how the
 WebDAV extensions interoperate with existing authentication schemes,
 and should make recommendations for using those schemes.
 5.11.2. Access Control. Access control requirements are specified in
 a separate access control work in progress [AC].
 5.11.3. Interoperability with Security Protocols. The WebDAV
 specification must provide a minimal list of security protocols which
 any compliant server / client must support.  These protocols should
 insure the authenticity of messages and the privacy and integrity of
 messages in transit.

5.12. Internationalization

5.12.1. Character Sets and Languages

 Since Web distributed authoring occurs in a multi-lingual
 environment, information intended for user comprehension must conform
 to the IETF Character Set Policy [CHAR].  This policy addresses
 character sets and encodings, and language tagging.

5.12.2. Rationale

 In the international environment of the Internet, it is important to
 insure that any information intended for user comprehension can be
 displayed in a writing system and language agreeable to both the
 client and the server. The information encompassed by this
 requirement includes not only the content of resources, but also such
 things as display names and descriptions of properties, property
 values, and status messages.

6. Acknowledgements

 Our understanding of these issues has emerged as the result of much
 thoughtful discussion, email, and assistance by many people, who
 deserve recognition for their effort.

Slein, et. al. Informational [Page 17] RFC 2291 Distributed Authoring and Versioning February 1998

 Terry Allen,
 Alan Babich, FileNet,
 Dylan Barrell, Open Text,
 Barbara Bazemore, PC DOCS,
 Martin Cagan, Continuus Software,
 Steve Carter, Novell,
 Dan Connolly, World Wide Web Consortium,
 Jim Cunningham, Netscape,
 Ron Daniel Jr., Los Alamos National Laboratory,
 Mark Day, Lotus,
 Martin J. Duerst,
 Asad Faizi, Netscape,
 Ron Fein, Microsoft,
 David Fiander, Mortice Kern Systems,
 Roy Fielding, U.C. Irvine,
 Mark Fisher, Thomson Consumer Electronics,
 Yaron Y. Goland, Microsoft,
 Phill Hallam-Baker, MIT,
 Dennis Hamilton, Xerox PARC,
 Andre van der Hoek, University of Colorado, Boulder,
 Del Jensen, Novell,
 Gail Kaiser, Columbia University,
 Rohit Khare, World Wide Web Consortium,
 Ora Lassila, Nokia Research Center,
 Ben Laurie, A.L. Digital,
 Mike Little, Bellcore,
 Dave Long, America Online,
 Larry Masinter, Xerox PARC,
 Murray Maloney, SoftQuad,
 Jim Miller, World Wide Web Consortium,
 Howard S. Modell, Boeing,
 Keith Moore, University of Tennessee, Knoxville,
 Henrik Frystyk Nielsen, World Wide Web Consortium,
 Jon Radoff, NovaLink,
 Alan Robertson,
 Henry Sanders, Microsoft,
 Andrew Schulert, Microsoft,
 Christopher Seiwald, Perforce Software,
 Einar Stefferud,
 Richard Taylor, U.C. Irvine,
 Robert Thau, MIT,
 Sankar Virdhagriswaran,
 Dan Whelan, FileNet, dan@FILENET.COM
 Gregory J. Woodhouse,

Slein, et. al. Informational [Page 18] RFC 2291 Distributed Authoring and Versioning February 1998

7. References

 [AC] J. Radoff, "Requirements for Access Control within Distributed
 Authoring and Versioning Environments on the World Wide Web",
 unpublished manuscript, <
 [CHAR] Alvestrand, H., "IETF Policy on Character Sets and Languages",
 RFC 2277, January 1998.
 [CM] P. Feiler, "Configuration Management Models in Commercial
 Environments", Software Engineering Institute Technical Report
 [HTML] Berners-Lee, T., and  D. Connolly, "HyperText Markup Language
 Specification - 2.0", RFC 1866, November 1995.
 [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
 January 1997.
 [ISO 10646] ISO/IEC 10646-1:1993. "International Standard --
 Information Technology -- Universal Multiple-Octet Coded Character
 Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane."
 [URL] Berners-Lee, T., Masinter, L., and M. McCahill. "Uniform
 Resource Locators (URL)", RFC 1738, December 1994.
 [VSE] A. Haake, D. Hicks, "VerSE: Towards Hypertext Versioning
 Styles", Proc. Hypertext'96, The Seventh ACM Conference on Hypertext,
 1996, pages 224-234.

Slein, et. al. Informational [Page 19] RFC 2291 Distributed Authoring and Versioning February 1998

8. Authors' Addresses

 Judith Slein
 Xerox Corporation
 800 Phillips Road 128-29E
 Webster, NY 14580
 Fabio Vitali
 Department of Computer Science
 University of Bologna
 E. James Whitehead, Jr.
 Department of Information and Computer Science
 University of California
 Irvine, CA 92697-3425
 Fax: 714-824-4056
 David G. Durand
 Department of Computer Science
 Boston University
 Boston, MA

Slein, et. al. Informational [Page 20] RFC 2291 Distributed Authoring and Versioning February 1998

9. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an

Slein, et. al. Informational [Page 21]

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