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.

Abstract

  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



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  possible that a single mechanism could simultaneously satisfy several
  requirements.

  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
  protocol.

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
  service.

  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:

       Properties
       Links
       Locking
       Reservations
       Retrieval of Unprocessed Source
       Partial Write
       Name Space Manipulation
       Collections



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       Versioning
       Variants
       Security
       Internationalization

3. Terminology

  Where there is overlap, usage is intended to be consistent with that
  in the HTTP 1.1 specification [HTTP].

  Client
       A program which issues HTTP requests and accepts responses.

  Collection
       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.

  Entity
       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.

  Link
       A typed connection between two or more resources.

  Lock
       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.

  Property
       Named descriptive information about a resource.

  Reservation
       A declaration that one intends to edit a resource.




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  Resource
       A network data object or service that can be identified by a
       URI.

  Server
       A program which receives and responds to HTTP requests.

  User Agent
       The client that initiates a request.

  Variant
       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
  functionality.

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.











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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
  extensions.

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.







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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





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  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
  types.

5.3. Locking

5.3.1. General Principles

  5.3.1.1. 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.

  5.3.1.2. 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
  resources.

5.3.2. Functional Requirements

  5.3.2.1. Write Locks. It must be possible to restrict modification of
  a resource to a specific person.

  5.3.2.2. Lock Query. It must be possible to find out whether a given
  resource has any active locks, and if so, who holds those locks.

  5.3.2.3. 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




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  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

  5.4.1.1. 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.

  5.4.1.2. Reservation Query. It must be possible to find out whether a
  given resource has any active reservations, and if so, who currently
  holds reservations.

  5.4.1.3. Release Reservation.  It must be possible to release the
  reservation.

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.








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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
  format.

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
  resource.

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.









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5.7. Name Space Manipulation

5.7.1. Copy

5.7.1.1. 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.

5.7.1.2. 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

5.7.2.1. 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.

5.7.2.2. 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
  itself.



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5.8.1. Functional Requirements

  5.8.1.1. List Collection. A listing of all resources in a specific
  collection must be accessible.

  5.8.1.2. Make Collection. It must be possible to create a new
  collection.

  5.8.1.3. Add to Collection.  It must be possible to add a resource to
  a collection directly or by reference.

  5.8.1.4. 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





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  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

  5.9.1.1. 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.

  5.9.1.2. 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




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  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.

  5.9.1.3. 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.

  5.9.1.4. 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.

  5.9.1.5. It is possible to version resources of any media type.

5.9.2. Functional Requirements

  5.9.2.1. 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
  required.



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  5.9.2.2. 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.

  5.9.2.3. 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
  graph.

  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.

  5.9.2.4. 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.

  5.9.2.5. 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.

  5.9.2.6. 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.




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       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.

  5.9.2.7. 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.

  5.9.2.8. 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.

  5.9.2.9. A version identifier must be unique across a version graph.

  5.9.2.10. 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.

  5.9.2.11. 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
  benefits:

  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.






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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
  operation.

  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
  history.

5.10. Variants

  Detailed requirements for variants will be developed in a separate
  document.

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



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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.





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RFC 2291          Distributed Authoring and Versioning     February 1998


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






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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, <http://lists.w3.org/Archives/Public/w3c-
  dist-auth/1997AprJun/0183.html>

  [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
  CMU/SEI-91-TR-7,
  <http://www.sei.cmu.edu/products/publications/91.reports/91.tr.007.html>

  [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.



















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RFC 2291          Distributed Authoring and Versioning     February 1998


8. Authors' Addresses

  Judith Slein
  Xerox Corporation
  800 Phillips Road 128-29E
  Webster, NY 14580

  EMail: [email protected]


  Fabio Vitali
  Department of Computer Science
  University of Bologna
  ITALY

  EMail: [email protected]


  E. James Whitehead, Jr.
  Department of Information and Computer Science
  University of California
  Irvine, CA 92697-3425

  Fax: 714-824-4056
  EMail: [email protected]


  David G. Durand
  Department of Computer Science
  Boston University
  Boston, MA

  EMail: [email protected]


















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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
  English.

  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
  "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.
























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