1. 1 WebDAV and DeltaV: Collaborative Authoring, Versioning, and Configuration Management for the Web Jim Whitehead University of California, Santa Cruz ejw@soe.ucsc.edu

2. 2 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

3. 3 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

4. 4 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

5. 5 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

6. 6 Application Use of WebDAV ClientServer File… Open LOCK Lock resource PROPFIND Send properties to client GET Send resource contents to client Edit PUT File… Save Exit UNLOCK Save new contents Unlock resource

7. 7 Collaborative Document Authoring  Three collaborators, in different cities, use Word 2000 to collaborate on a report they are producing together.

8. 8 Collaborative Web Site Authoring  Two homes each develop their family Web site using WebDAV to interact with their ISP.

9. 9 Remote Authoring, Part of Staged Production

10. 10 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!

11. 11 Filesystem View  Exemplars: Web Folders, WebDrive, WebIFS, TeamDrive, Mac OS X

12. 12 Document Authoring  Exemplars: Office 2000/XP: Word, Excel, PowerPoint, as well as Photoshop, Documentor, and XML Spy Office: uses filesystem metaphor for WebDAV location

13. 13 Photoshop  Workflow metaphor for WebDAV location

14. 14 Web Site Authoring  Exemplars: Go Live 5, Macromedia Director  Site metaphor for WebDAV location

15. 15 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)

16. 16 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

17. 17 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

18. 18 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.

19. 19 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

20. 20 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

21. 21 Access Control Infrastructure  Access Control:  The ability to remotely control who can read and write a resource  Key challenge:  Expose the access control capabilities of the repository…  …while ensuring the client-side user interface can be simple (I.e., avoid lots of feature discovery)  Access control lists  Each entry grants/denies a privilege to a principal (or group)  Infrastructure for remotely creating collaboration groups

22. 22 Searching Infrastructure  Searching a WebDAV repository - DASL:  Search for resources with a given property, or a given property value  Search for a substring inside a resource body  Search scope can be one resource, a collection of resources, a hierarchy of resources, or a whole server  Search syntax is extensible  Search specification specified as body submitted with SEARCH command  Could accommodate XML Query syntax  Infrastructure for remote searching

23. 23 WebDAV Methods and Data Model

24. 24 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

25. 25 Scope of WebDAV Methods Web Resource Body (primary state) Properties (name, value) pairs LOCK UNLOCK COPY MOVE † DELETE † MKCOL † (PUT † ) PROPFIND PROPPATCH † GET PUT † † - affected by LOCK

26. 26 DeltaV: Versioning and Configuration Management

27. 27 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.

28. 28 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

29. 29 Version History Foo.htm 1 2 7 6 5 4 3 initial Beta1 Test1 Beta2 URL path of Versioned Controlled Resource Version Name Label Successor Line of Descent Revision History Predecessor Branch Merge

30. 30 Representation of a Version History

31. 31 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

32. 32 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.

33. 33 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

34. 34 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

35. 35 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

36. 36 Server Workspace Example  Version history of main.c: 1234 /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

37. 37 Server Workspace Example main.c 2 makefile 3 1 4 2 3 1 defs.h 2 1 /users/chris/projectX/ main.c, 4 makefile, 3 defs.h, 3 /users/geoff/projectX/ main.c, 5 makefile, 3 defs.h, 2 3 5

38. 38 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

39. 39 WebDAV Projects at UC Santa Cruz

40. 40 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  Libby Miller, ILRT (RDF work)  http://www.cse.ucsc.edu/~marick/

41. 41 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

42. 42 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

43. 43 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

44. 44 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

45. 45 WebDAV Resources

46. 46 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.

47. 47 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

48. 48 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

49. 49 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.

50. 50 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.

51. 51 Document Roadmap Distributed Authoring Locking, Properties, Copy/Move RFC 2518 complete Versioning & CM Protocol just sent to IESG Finish: Fall 2001 Advanced Collections Requirements and protocol for bindings, redirectors, ordered coll. Finish: December 2001 Access Control Protocol for remote access control Finish: Fall 2001 WebDAV Working Group: DASL: Searching Requirements and protocol for searching a WebDAV repository Finish: mid 2002 Delta-V Working Group:

52. 52