WebDAV and DeltaV:
Collaborative Authoring, Versioning,
and Configuration Management
for the Web
Jim Whitehead
University of California, Santa Cruz
ejw@soe.ucsc.edu
1
WebDAV and DeltaV
 WebDAV and DeltaV are:
 Application layer network protocols
 Extensions to the Hypertext Transfer Protocol (HTTP 1.1)
 Developed by the Internet Engineering Task Force (IETF)
 WebDAV
 Remote collaborative authoring of Web resources
 Overwrite prevention, metadata management, namespace
operations
 DeltaV
 Versioning and Configuration Management
 Extends base WebDAV capabilities
 Checkout/checkin, version history, logical change tracking,
workspaces, configuration management
2
Major WebDAV Clients
 Application Software:
 Microsoft: Office 2000/XP (Word, Excel, PowerPoint, Publisher)
 Adobe: Photoshop 6, Acrobat 5
 Web Site Authoring
 Adobe: Go Live 5
 Macromedia: Dreamweaver 4
 Remote File Access:
 Apple: Mac OS X webdavfs
 OS X also ships with Apache and mod_dav (have to configure mod_dav
to make it work)





Microsoft: Windows Web Folders
Wind River Software: WebDrive
Goliath (Mac, open source)
Nautilus (GNOME project, Eazel)
WebDAV Explorer (UC Irvine, Feise/Kanomata, open source)
 XML editors
 Excosoft: Documentor
 Altova: XML Spy 3.5
3
Major WebDAV Servers
Microsoft: IIS 5/6, Exchange 2000, Sharepoint
Apache: mod_dav (over 10,000 sites)
Oracle: Internet File System
Adobe: InScope
Xythos: Web File Server
Novell: Netware 5.1, Net Publisher
W3C: Jigsaw
Endeavors: Magi-DAV
IBM: DAV4J (DeveloperWorks)
DataChannel: DataChannel Server (DCS 4.1)
Intraspect: 4i
OpenLink: Virtuoso
Hyperwave: Information Server 5.5
4
Using WebDAV
 You have to produce an XML document
 Fire up your favorite XML processor & start editing
 You decide to bring on another author
 Using the same XML processor, save to the Web
 Give your collaborator the URL of the XML document
 Start collaboration on the document by editing in-place on
the Web
 A seamless transition from individual to
collaborative work
5
Application Use of WebDAV
Client
File… Open
LOCK
PROPFIND
GET
Edit
File… Save
Exit
PUT
UNLOCK
Server
Lock resource
Send properties
to client
Send resource
contents to client
Save new contents
Unlock resource
6
Collaborative Document Authoring
 Three collaborators, in different cities, use Word 2000
to collaborate on a report they are producing
together.
BOSTON
LOS ANGELES
TOKYO
Katrina
Johnathan
Kenji
Word
2000
Word
2000
Word
2000
HTTP/DAV
HTTP/DAV
WebDAV
server
shared document
HTTP/DAV
A
7
Collaborative Web Site Authoring
 Two homes each develop their family Web site using
WebDAV to interact with their ISP.
HOME 1
INTERNET SERVICE PROVIDER
Joe
Homeuser
Go
Live 5
Go
Live 5
Joe’s
Daughter
WebDAV
server
Jane
McPC
HTTP/DAV
HTTP/DAV
/joe
/html
/images
HOME 2
Dream
Weaver
4
/jane
/html
/images
Jane’s web site
Web site for Joe and
his daughter
8
Remote Authoring, Part of Staged
Production
CHICAGO
SEOUL
Cindy
Yung Kim
Acrobat
5
Go Live
5
FRANKFURT
Hartmut
Photo
shop 6
Frank
HTTP/DAV
Excel
2000
HTTP/DAV
General Internet Readers
HTTP
server
production
server
HTTP/DAV
WebDAV
server
contributions
server
web site
contents
/contrib
project
Web site
/chicago
/seoul
firewall
/frankfrt
HTTP
server
Web site development team
incorporates contributions
submitted to the contributions
server.
development
server
web site
contents
9
Visions for WebDAV
 Participants in WebDAV have many views on what it is:
 A protocol for collaborative authoring of all document types
 XML, HTML, word processing, spreadsheets,
 A Web-based network file system, with nice high-latency behavior
 Better performance than NFS and Samba over the Internet
 A data integration technology for accessing a wide range of
repositories
 Document mgmt. systems, configuration mgmt. systems, filesystems,
etc.
 Remote software engineering infrastructure
 A replacement protocol that can handle email, calendaring,
directory lookup and more
 Could replace: POP, IMAP, CAP, LDAP…
 All views are correct!
10
Filesystem View
 Exemplars: Web Folders, WebDrive, WebIFS,
TeamDrive, Mac OS X
11
Document Authoring
 Exemplars: Office 2000/XP: Word, Excel, PowerPoint,
as well as Photoshop, Documentor, and XML Spy
Office: uses filesystem
metaphor for WebDAV location
12
Photoshop
 Workflow metaphor for WebDAV location
13
Web Site Authoring
 Exemplars: Go Live 5, Macromedia Director
 Site metaphor for WebDAV location
14
Remote Collaborative Annotation
 Acrobat 5 views a WebDAV location as a storage location for
document annotations
 Annotations are stored in resources separate from the PDF
document
 One collection per document
 One annotation resource per user (in collection)
15
Email Access via WebDAV
 Outlook Web Access for Exchange 2000 uses WebDAV
 plus some non-standard “batch” methods, for efficiency
 Client is DHTML running in the browser
16
Facets of WEBDAV
 There are many ways to view the DAV work:





Collaboration infrastructure
Metadata repository infrastructure
Namespace management infrastructure
Access control infrastructure
Searching infrastructure – DASL
17
Collaboration Infrastructure
 Whole resource locking supports:
 remote collaborative authoring of any media type
 Web pages, Word processing, Presentations, XML, …
 Lock characteristics:
 Long-duration locks
 Not associated with network connection
 Client receives a lock token identifying the lock
 Can disconnect from network after receiving lock token
 Locks automatically expire after a client specified
timeout period
 Lock single resources, or hierarchies of resources
 Infrastructure for asynchronous, widely
distributed, hypertext-aware, collaborative
editing tools.
18
Metadata Recording Infrastructure
 Metadata support
 Properties are (name, value) pairs that can be
created, modified, deleted, and read on Web
resources.
 Consistency of properties can be maintained by
the server or the client
 Property values are well-formed Extensible Markup
Language (XML)
 Can store RDF as well
 Property name is a URI or URL
 Extensible, global property namespace
 Infrastructure for recording information about
Web data
 A general purpose metadata repository
19
Namespace Management
Infrastructure
 Remote name space management:
 Copy and Move
 individual resources
 hierarchies of resources
 to/from a locked hierarchy
 Create and modify collections of resources
 Retrieve listings of collection members
 Useful for creating Save…As dialog boxes
 Adds hierarchical navigation to the Web
 Augments hypertext navigation and searching
 Infrastructure for remotely organizing and
viewing collections of Web resources
20
WebDAV Methods
 Overwrite Prevention:
 LOCK – prevents non-lock holders from writing to the
resource
 UNLOCK – removes a lock
 Metadata Management:
 PROPFIND – read properties from a resource
 Allprop – all property names and values
 Propname – only return property names
 Prop – just return specified properties
 PROPPATCH – write properties on a resource
 Namespace Management
 COPY – duplicate a resource
 MOVE – move a resource (preserving identity)
 MKCOL – create a new collection
24
Scope of WebDAV Methods
Web Resource
LOCK
UNLOCK
COPY
MOVE†
DELETE†
MKCOL†
(PUT†)
Properties
(name, value)
pairs
PROPFIND
Body
(primary
state)
GET
PROPPATCH†
PUT†
† - affected by
LOCK
25
DeltaV: Versioning and
Configuration Management
26
Remote Collaborative Document
Authoring Scenarios
 A task force of people from geographically dispersed
business units need to develop a report together.
 Team needs to solicit feedback, so they send out copies of
the report.
 As a result, the team needs a permanent copy of the exact
report version they are having other people review.
BOSTON
LONDON
TOKYO
Rebecca
Johnathan
Kenji
Word
2000
Word
2000
Word
2000
DAV/DeltaV
DAV/DeltaV
DAV/DeltaV
DAV/DeltaV
server
auto-versioning
enabled
shared document
A
A
v1
v2
A
v3
27
What is DeltaV?
 DeltaV is:
 An application layer network protocol
 Extends the WebDAV protocol
 WebDAV itself extends HTTP 1.1
 Thus DeltaV is also an extension to HTTP 1.1
 HTTP is the core network protocol of the Web
 An interoperability standard
 Allows document authoring and software development
applications to interoperate with versioning and configuration
management systems using a common interface
 A data model
 DeltaV embodies a data model that is capable of modeling
multiple versioning and configuration management repositories
 The data model is independent of network protocol
 A data integration infrastructure
 A common place for cross-application data sharing
28
Version History
URL path of
Versioned
Controlled
Resource
Foo.htm
initial 1
Beta1
Branch
Version
Name
Label
Successor
Test1
2
3
4
5
6
Line of
Descent
Revision
History
Merge
Beta2
7
Predecessor
29
Representation of a Version History
Abstract version
history of foo.html
Representation of foo.html in DeltaV
version history resource
v1
v2
version-controlled resource
DAV:version-set
 /his/73/ver/1
 /his/73/ver/2
 /his/73/ver/3
DAV:checked-out
 /his/73/ver/3
DAV:version-history
 /his/73/vhr
DAV:root-version
 /his/73/ver/1
body of
version v3
/his/73/vhr
v3
/foo.html
v1
v2
v3
/his/73/ver/1
/his/73/ver/2
/his/73/ver/3
version resources
30
Unique Aspects of Versioning Data
Model
 DeltaV data model is different from RCS/SCCS model
 RCS: placing foo.html under version control causes:
 foo.html to be made read-only
 Creation of RCS/foo.html,v archive file
 Archive contains version history and version data
 Differences
 Both use the original name as the place where commands are
directed
 But, version-controlled resource has more metadata
 DeltaV separates version history from version storage
 DeltaV gives each version a unique identifier (URL)
 Note that delta storage can still be used in the underlying
repository
31
Rationale for Versioning Data Model
 Each version is given its own URL, thus allowing
hypertext linking to a specific version.
 Hence, each version must be a separate resource
 Workspaces are the motivation for separating the
version-controlled resource from the history resource.
 A workspace allows a collaborator to work in isolation, in
their own part of the namespace.
 For example, Greg and Lisa might have workspaces:
 /ws/users/greg/ and /ws/users/lisa/
 If both want foo.html to appear in their local workspace,
each needs a version controlled resource.
 Thus, one version history can be associated with multiple
version controlled resources.
32
Autoversioning

There are many WebDAV-aware applications



They know nothing about versioning!
Would like to provide automatic versioning support
Two styles of autoversioning:
1. Every modification creates a new version


PUT/PROPPATCH  CHECKOUT  PUT/PROPPATCH 
CHECKIN
Works best for authoring clients that replicate resources to a
local disk, and only write to the server at the end of an editing
session.
2. Every LOCK/UNLOCK pair creates a new version




LOCK  LOCK  CHECKOUT
UNLOCK  CHECKIN  UNLOCK
Works well for authoring clients that work directly on the
WebDAV server and take out locks, like Office 2000.
Style is controlled by DAV:autocheckout and
DAV:autocheckin properties on version controlled resource
33
Activities
 Frequently, a logical change spans multiple versions in
multiple version histories
 For example, fixing a specific software bug can involve the
creation of multiple versions of several files
 Activities associate a logical change with the set of
versions created while making that change.
 Versions from a given version history are limited to a
single line of descent
 Activities are not versioned
 Sometimes want to ensure that all work done by team
members is on a single line of descent
 Avoids merging between team members
 Activities can be used to enforce working on just a single line
of descent
34
Workspaces

A workspace is a location…




… where a person can work in isolation
… from ongoing changes made by other collaborators
to the same set of resources.
Workspace use scenarios:


Two people each modify a common source code file, and
want to test their work before integrating changes
The directory structure of a large project is being changed



Don’t want to require everyone to stop working while this
takes place
Keep namespace changes invisible to team until complete
A developer is trying a change that might not pan out

New files are in their workspace, but not under version control
until the final viability of the change is known
35
Server Workspace Example
 Version history of main.c:
version controlled resources
version history resource
/projectX/main.c
/users/chris/
projectX/main.c
/users/geoff/
projectX/main.c
/repo/o522/v1
/repo/o522/v2
/his/o522
/repo/o522/v3
/repo/o522/v4
1
2
3
4
5
/repo/o522/v1 /repo/o522/v2 /repo/o522/v3 /repo/o522/v4 /repo/o522/v5
version resources
36
Server Workspace Example
main.c makefile defs.h
1
1
1
2
2
2
3
3
3
4
/users/geoff/projectX/
main.c, 5
makefile, 3
defs.h, 2
/users/chris/projectX/
main.c, 4
makefile, 3
defs.h, 3
5
37
Baselines
 When a large collection of documents is released
outside the developing organization, there is a need
to record exactly which document versions were
released.
 Especially true for software project releases
 A baseline can record the exact version of a large set
of resources under version control
 Baselines can also be used for recording intermediate
project states
 The state of the project as of last Friday
 Quality assurance can then have a stable snapshot to work from
 Baselines are used to perform configuration
management
38
WebDAV Projects
at UC Santa Cruz
39
DAV Calendaring and Scheduling
 Problems:
 iCal data format is complex and difficult to understand
 Few network effects with other data formats
 Compare with XML-based formats
 A separate protocol is under development for remote
collaborative calendaring and scheduling
 Requirements are not significantly different from WebDAV
 Approach:
 Translate iCal data format to Resource Description
Framework (RDF)
 Develop profile for using WebDAV to remotely author
calendar event resources
 Prototype ideas using Gnome Calendar application
 Work performed by:
 Michael Arick, UCSC <marick@soe.ucsc.edu>
 Libby Miller, ILRT <libby.miller@bristol.ac.uk> (RDF work)
 http://www.cse.ucsc.edu/~marick/
40
SOAP over DAV
 SOAP: Simple Object Access Protocol
 An XML-based remote procedure call protocol
 Typically marshalled as an XML body to an HTTP POST request
 Problem:
 SOAP assumes the response will come back quickly (1-2 minutes at
most)
 Not suitable for long-duration transactions
 No versioning of interfaces
 Approach:
 Marshall SOAP messages using PROPPATCH/PROPFIND
 Submit request  write to a property value
 Receive response  read a property value
 Can leverage versioning, access control, metadata, searching
facilities of WebDAV
 Work performed by Elias Sinderson <elias@cse.ucsc.edu>
41
Electronic Records Management
 US Government agencies are required to support
standard DoD 5015.2
 Describes metadata items useful for archiving electronic
records
 5015.2 is not an interoperability standard
 Approach
 Develop an XML representation of 5015.2 metadata items
 Store 5015.2 metadata in WebDAV properties
 Develop server support for
 automatic archiving/disposal of records
 automatic setting of 5015.2 property values
 Develop client support for entry/viewing/searching 5015.2
items
 Payoff
 Wide deployment of interoperable, low-cost infrastructure for
archiving electronic records
 Work performed by Lan Xue <lanxue@soe.ucsc.edu>
42
Study Wish List
 How are people actually using WebDAV technology?
 Many stories of people using it for file sharing
 Less evidence of collaborative authoring use
 In particular, Go Live and Director are designed for
group use
 How are people using the collaboration facilities?
 WebDAV has relatively poor awareness support –does this
affect use?
 How is the technology used differently in different
organizational settings?
 We finally have a remote collaboration technology
that is starting to be broadly used
 We can now test many long-held assumptions about this
technology
43
Project Wish List
 DAVCam
 A digital camera that takes a picture…
 Automatically writes the picture to a DAV store
 Allows voice-to-text annotation of photo with metadata
 Open Hypertext integration
 Export hypertext links as Xlinks in DAV properties
 Allow authoring of links via these properties
 Mapping to OHP Storage interface
 DAV as storage layer for spatial hypertext
 Is DAV sufficient by itself? Or are additional capabilities or
optimizations needed?
 DAV-based Weblog (“blog”) system
 Author content via DAV
44
WebDAV Resources
45
WebDAV
 WebDAV Resources
 http://www.webdav.org/
 A central collection of pages and links to all things WebDAV.
 WebDAV Working Group
 http://www.ics.uci.edu/pub/ietf/webdav/
 Contains links to active documents, and a complete list of WebDAVsupporting applications.
 RFC 2518 – WebDAV Distributed Authoring Protocol
 http://www.ics.uci.edu/pub/ietf/webdav/protocol/rfc2518.pdf
 This is the WebDAV Distributed Authoring Protocol specification
 WebDAV: A network protocol for remote collaborative
authoring on the Web
 Proc. of the Sixth European Conference on Computer-Supported
Cooperative Work, Sept. 12-16, 1999, Copenhagen, Denmark, pp.
291-310.
 http://www.ics.uci.edu/~ejw/papers/dav-ecscw.pdf
 An academic paper giving an overview of the WebDAV Distributed
Authoring Protocol.
46
DeltaV
 Delta-V Working Group web page
 http://www.webdav.org/deltav/
 The home page for the IETF Delta-V Working Group, with links off to
the most recent specifications.
 G. Clemm, J. Amsden, C. Kaler, J. Whitehead, “Versioning
Extensions to WebDAV”, Internet-Draft, work-in-progress,
draft-ietf-deltav-versioning-16, July 3, 2001.
 http://www.webdav.org/deltav/protocol/draft-ietf-deltav-versioning16.htm
 The most recent revision of the versioning and configuration
management protocol specification.
 The Future of Distributed Software Development on the
Internet
 Web Techniques, Vol. 4, No. 10, October, 1999, pages 57-63
 http://www.webtechniques.com/archives/1999/10/whitehead/
 An introduction to WebDAV and DeltaV that describes the advantages of
DeltaV over CVS for remote collaborative software development
47
DASL: DAV Searching & Locating
 DAV Searching and Locating page
 http://www.webdav.org/dasl/
 A web site containing links to the most recent WebDAV
searching protocol specifications.
 A. Babich, J. Davis, R. Henderson, D. Lowry, Sa.
Reddy, Su. Reddy, “DAV Searching and Locating”,
work-in-progress.
 http://www.webdav.org/dasl/protocol/draft-davis-daslprotocol-00.html
 The most recently edited DASL protocol specification. This
document was never submitted as an Internet-Draft.
 Will be submitted for consideration as an Experimental RFC in
the near future.
 In 1-2 years, will be submitted as a Proposed Standard
48
Access Control Protocol
 Access Control page
 http://www.webdav.org/acl/
 A web site containing links to current access control protocol
specifications.
 WebDAV Access Control Protocol
 draft-ietf-webdav-acl-06, June 21, 2001.
 http://www.webdav.org/acl/protocol/draft-ietf-webdav-acl06.htm
 The most recent revision of the access control protocol
specification.
49
Advanced Collections
 WebDAV Bindings
 draft-ietf-webdav-binding-protocol-02, December 17, 1999.
 http://www.ics.uci.edu/pub/ietf/webdav/collection/draft-ietfwebdav-binding-protocol-02.txt
 The most recent revision of the WebDAV Bindings Protocol.
 WebDAV Redirect Reference Resources
 draft-ietf-webdav-redirectref-protocol-02, December 17,
1999.
 http://www.ics.uci.edu/pub/ietf/webdav/collection/draft-ietfwebdav-redirectref-protocol-02.txt
 The most recent revision of the Redirect Resources protocol.
 WebDAV Ordered Collections Protocol
 draft-ietf-webdav-ordering-protocol-02, December 20, 1999.
 http://www.ics.uci.edu/pub/ietf/webdav/collection/draft-ietfwebdav-ordering-protocol-02.txt
 The most recent revision of the Ordered Collections protocol.
50
Document Roadmap
WebDAV Working Group:
Distributed Authoring
Locking, Properties, Copy/Move
RFC 2518 complete
Access Control
Protocol for remote access control
Finish: Fall 2001
Advanced Collections
Requirements and protocol for
bindings, redirectors, ordered coll.
Finish: December 2001
DASL:
Searching
Requirements and protocol for
searching a WebDAV repository
Finish: mid 2002
Delta-V Working Group:
Versioning & CM
Protocol just sent to IESG
Finish: Fall 2001
51
52