1 webdav and deltav: collaborative authoring, versioning, and configuration management for the web...
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WebDAV and DeltaV: Collaborative Authoring, Versioning,
and Configuration Management for the Web
Jim WhiteheadUniversity of California, Santa [email protected]
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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
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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
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Major WebDAV Servers
Microsoft: IIS 5/6, Exchange 2000, SharepointApache: mod_dav (over 10,000 sites)Oracle: Internet File SystemAdobe: InScopeXythos: Web File ServerNovell: Netware 5.1, Net PublisherW3C: JigsawEndeavors: Magi-DAVIBM: DAV4J (DeveloperWorks)DataChannel: DataChannel Server (DCS 4.1)Intraspect: 4iOpenLink: VirtuosoHyperwave: Information Server 5.5
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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
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Application Use of WebDAV
Client Server
File… Open LOCKLock resource
PROPFIND
Send properties to client
GET
Send resourcecontents to clientEdit
PUT
File… Save
Exit UNLOCK
Save new contents
Unlock resource
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Collaborative Document Authoring
Three collaborators, in different cities, use Word 2000 to collaborate on a report they are producing together.
WebDAV server
A
Johnathan
Word 2000
BOSTON LOS ANGELES
shared document
Katrina Word 2000
TOKYO
Kenji
Word 2000
HTTP/DAV HTTP/DAV
HTTP/DAV
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Collaborative Web Site Authoring
Two homes each develop their family Web site using WebDAV to interact with their ISP.
WebDAV server
Joe Homeuser Go Live 5
/joe
/html /images
HTTP/DAV
INTERNET SERVICE PROVIDER HOME 1
/jane
/html /images
Jane McPC DreamWeaver
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HTTP/DAV
Jane’s web site
HOME 2
Joe’s Daughter
Go Live 5
Web site for Joe and his daughter
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Remote Authoring, Part of Staged Production
WebDAV server
Frank
Excel 2000
CHICAGO SEOUL
Yung Kim Go Live
5
FRANKFURT
Hartmut
Photo shop 6
HTTP/DAV HTTP/DAV
HTTP/DAV
/contrib
/seoul /frankfrt project Web site
Cindy
Acrobat 5
/chicago
contributions server
HTTP server
development server
web site contents
Web site development team incorporates contributions submitted to the contributions server.
HTTP server
web site contents
General Internet Readers
firewall
production server
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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!
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Filesystem View
Exemplars: Web Folders, WebDrive, WebIFS, TeamDrive, Mac OS X
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Document Authoring Exemplars: Office 2000/XP: Word, Excel, PowerPoint,
as well as Photoshop, Documentor, and XML Spy
Office: uses filesystem metaphor for WebDAV location
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Photoshop Workflow metaphor for WebDAV location
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Web Site Authoring Exemplars: Go Live 5, Macromedia Director Site metaphor for WebDAV location
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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)
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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
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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
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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.
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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
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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
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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
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Scope of WebDAV Methods
Web Resource
Body(primary
state)
Properties(name, value)
pairsLOCKUNLOCKCOPYMOVE†
DELETE†
MKCOL†
(PUT†)
PROPFIND
PROPPATCH†
GET
PUT†
† - affected by
LOCK
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DeltaV: Versioning and Configuration Management
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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.
DAV/DeltaV server
A
Johnathan
Word 2000
BOSTON LONDON
shared document
Rebecca
Word 2000
TOKYO
Kenji
Word 2000
DAV/DeltaV DAV/DeltaV
DAV/DeltaV
A A
v1 v2 v3
auto-versioning enabled
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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
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Version History
Foo.htm
1
2
7
65
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initial
Beta1
Test1
Beta2
URL path of VersionedControlledResource
Version Name
Label
Successor
Line ofDescent
RevisionHistory
Predecessor
Branch
Merge
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Representation of a Version History
v1
v2
v3
Abstract version history of foo.html
Representation of foo.html in DeltaV
v1 v2 v3
version resources
body of version v3
/his/73/ver/1 /his/73/ver/2 /his/73/ver/3
version-controlled resource
/foo.html
DAV:checked-out /his/73/ver/3
version history resource
DAV:version-history /his/73/vhr
/his/73/vhr
DAV:version-set /his/73/ver/1 /his/73/ver/2 /his/73/ver/3
DAV:root-version /his/73/ver/1
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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
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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.
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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
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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
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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
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Server Workspace Example Version history of main.c:
1 2 3 4
/repo/o522/v1
/repo/o522/v2
/repo/o522/v3
/repo/o522/v4
version history resource
/repo/o522/v1
/repo/o522/v2
/repo/o522/v3
/repo/o522/v4
version resources
/his/o522
/projectX/main.c
/users/chris/ projectX/main.c
/users/geoff/ projectX/main.c
version controlled resources
5
/repo/o522/v5
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Server Workspace Example
main.c
2
makefile
3
1
4
2
3
1
defs.h
2
1
/users/chris/projectX/main.c, 4makefile, 3defs.h, 3
/users/geoff/projectX/main.c, 5makefile, 3defs.h, 2
3
5
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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
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WebDAV Projects at UC Santa Cruz
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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 <[email protected]> Libby Miller, ILRT <[email protected]> (RDF work) http://www.cse.ucsc.edu/~marick/
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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 <[email protected]>
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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
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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
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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
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WebDAV Resources
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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 WebDAV-supporting 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.
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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-
versioning-16.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
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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-dasl-
protocol-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
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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-acl-06.htm The most recent revision of the access control protocol
specification.
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Advanced Collections
WebDAV Bindings draft-ietf-webdav-binding-protocol-02, December 17, 1999. http://www.ics.uci.edu/pub/ietf/webdav/collection/draft-ietf-
webdav-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-ietf-
webdav-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-ietf-
webdav-ordering-protocol-02.txt The most recent revision of the Ordered Collections protocol.
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Document Roadmap
Distributed AuthoringLocking, Properties, Copy/MoveRFC 2518 complete
Versioning & CMProtocol just sent to IESGFinish: Fall 2001
Advanced CollectionsRequirements and protocol forbindings, redirectors, ordered coll.Finish: December 2001
Access ControlProtocol for remote access controlFinish: Fall 2001
WebDAV Working Group:
DASL:
SearchingRequirements and protocol forsearching a WebDAV repositoryFinish: mid 2002
Delta-V Working Group:
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