RFC2291 - Requirements for a Distributed Authoring and Versioning Protocol for t

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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.

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

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

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.

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.

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.

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

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

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.

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.

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.

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

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

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.

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.

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.

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

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.

Terry Allen, tallen@sonic.net
Alan Babich, FileNet, babich@filenet.com
Dylan Barrell, Open Text, dbarrell@opentext.ch
Barbara Bazemore, PC DOCS, barbarab@pcdocs.com
Martin Cagan, Continuus Software, Marty_Cagan@continuus.com
Steve Carter, Novell, srcarter@novell.com
Dan Connolly, World Wide Web Consortium, connolly@w3.org
Jim Cunningham, Netscape, jfc@netscape.com
Ron Daniel Jr., Los Alamos National Laboratory, rdaniel@lanl.gov
Mark Day, Lotus, Mark_Day@lotus.com
Martin J. Duerst, mduerst@ifi.unizh.ch
Asad Faizi, Netscape, asad@netscape.com
Ron Fein, Microsoft, ronfe@microsoft.com
David Fiander, Mortice Kern Systems, davidf@mks.com
Roy Fielding, U.C. Irvine, fielding@ics.uci.edu
Mark Fisher, Thomson Consumer Electronics, FisherM@indy.tce.com
Yaron Y. Goland, Microsoft, yarong@microsoft.com
Phill Hallam-Baker, MIT, hallam@ai.mit.edu
Dennis Hamilton, Xerox PARC, hamilton@parc.xerox.com
Andre van der Hoek, University of Colorado, Boulder,
andre@cs.colorado.edu
Del Jensen, Novell, dcjensen@novell.com
Gail Kaiser, Columbia University, kaiser@cs.columbia.edu
Rohit Khare, World Wide Web Consortium, khare@w3.org
Ora Lassila, Nokia Research Center, ora.lassila@research.nokia.com
Ben Laurie, A.L. Digital, ben@algroup.co.uk
Mike Little, Bellcore, little@bellcore.com
Dave Long, America Online, dave@sb.aol.com
Larry Masinter, Xerox PARC, masinter@parc.xerox.com
Murray Maloney, SoftQuad, murray@sq.com
Jim Miller, World Wide Web Consortium, jmiller@w3.org
Howard S. Modell, Boeing, howard.s.modell@boeing.com
Keith Moore, University of Tennessee, Knoxville, moore@cs.utk.edu
Henrik Frystyk Nielsen, World Wide Web Consortium, frystyk@w3.org
Jon Radoff, NovaLink, jradoff@novalink.com
Alan Robertson, alanr@bell-labs.com
Henry Sanders, Microsoft,
Andrew Schulert, Microsoft, andyschu@microsoft.com
Christopher Seiwald, Perforce Software, seiwald@perforce.com
Einar Stefferud, stef@nma.com
Richard Taylor, U.C. Irvine, taylor@ics.uci.edu
Robert Thau, MIT, rst@ai.mit.edu
Sankar Virdhagriswaran, sv@hunchuen.crystaliz.com
Dan Whelan, FileNet, dan@FILENET.COM
Gregory J. Woodhouse, gjw@wnetc.com

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",
RFC2277, 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", RFC1866, November 1995.

[HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC2068,
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)", RFC1738, 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.

8. Authors' Addresses

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

EMail: slein@wrc.xerox.com

Fabio Vitali
Department of Computer Science
University of Bologna
ITALY

EMail: fabio@cs.unibo.it

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

Fax: 714-824-4056
EMail: ejw@ics.uci.edu

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

EMail: dgd@cs.bu.edu

9. Full Copyright Statement

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

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