WebDAV and DeltaV: Collaborative Authoring, Versioning, and Configuration Management �for the Web

WebDAV and DeltaV: Collaborative Authoring, Versioning, and Configuration Management �for the Web

1. 1
WebDAV and DeltaV:
Collaborative Authoring, Versioning,
and Configuration Management
for the Web
Jim Whitehead
University of California, Santa
Cruz
[email protected]

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, Illustrator 10, Acrobat 5, In Design 2
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)
WebDAV Explorer (UC Irvine, Feise/Kanomata, open source)
XML editors
Excosoft: Documentor
Altova: XML Spy
SoftQuad: XMetal

4. 4
Major WebDAV Servers
Microsoft: IIS 5/6, Exchange 2000, Sharepoint
Apache: mod_dav (over 95,000 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)
FileNet: Panagon ECM
Intraspect: 4i
Merant: PVCS Dimensions, Content Manager
Hyperwave: Information Server 5.5
4D: WebSTAR V

5. 5
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

6. 6
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

Dream
Weaver
4
HTTP/DAV
Jane’s web site
HOME 2
Joe’s
Daughter

Go
Live 5
Web site for Joe and
his daughter

7. 7
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

8. 8
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!

9. 9
Filesystem View
Exemplars: Web Folders, WebDrive, WebIFS,
TeamDrive, Mac OS X

10. 10
Document Authoring
Exemplars: Office 2000/XP: Word, Excel, PowerPoint, as well
as Photoshop, Documentor, and XML Spy
Office: uses filesystem
metaphor for WebDAV location

11. 11
Photoshop
Workflow metaphor for WebDAV location

12. 12
Web Site Authoring
Exemplars: Go Live 5/6, Dreamweaver
Site metaphor for WebDAV location

13. 13
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)

14. 14
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

15. 15
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.

16. 16
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

17. 18
Access Control Infrastructure
Access Control:
The ability to remotely control who can read and write a
resource
Key challenges:
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)
Provide some notion of principal, without duplicating LDAP
Handle large numbers of principals
Access control lists
Each entry grants/denies a privilege to a principal (or group)
Infrastructure for remotely creating collaboration groups

18. 19
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

19. 20
WebDAV Methods
and Data Model

20. 21
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

21. 22
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

22. 23
DeltaV: Versioning and
Configuration Management

23. 24
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

24. 25
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 (RFC 3253)
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

25. 26
Version History
Foo.htm
1
2
7
65
43
initial
Beta1
Test1
Beta2
URL path of
Versioned
Controlled
Resource
Version
Name
Label
Successor
Line of
Descent
Revision
History
Predecessor
Branch
Merge

26. 27
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

27. 28
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

28. 29
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

29. 30
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

30. 31
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

31. 33
WebDAV Projects at
UC Santa Cruz

32. 34
Recontextualizing WebDAV
WebDAV and DeltaV gathered decontextualized
requirements for collaboration and version control
Abstracted away characteristics of specific application domains
Used Web authoring & software development as driving
problems
Led to a powerful, inexpensive, generic content
management capability
Now, goal is to apply the general-purpose capabilities
of WebDAV/DeltaV to solve specific problems:
Electronic records management
Digital libraries
… as well as ensuring they satisfy original goals:
Document management
Software development

33. 35
Advanced Document Collaboration
Infrastructure
Goal: Create advanced open-source WebDAV
server with following characteristics:
Highly scalable
store and search millions of documents
Data integration
knit together multiple document and metadata repositories
Access Postdoc, legacy stores via DAV/DeltaV
Access Control
support the emerging ACL protocol standard
Versioning
document versioning and auto-versioning support

34. 36
Advanced Document Collaboration
Infrastructure (2)

Peter

Word
NASA Ames NASA Goddard
Jason

Power
Point
JPL
Julia

Windows
Web Fldr
HTTP/DAV HTTP/DAV
HTTP/DAV
Postdoc
repository
SQL
database
legacy
metadata
store
Apache
mod_dav
mod_dav_repos
wrapper
wrapper
wrapper

35. 37
Advanced Document Collaboration
Infrastructure (3)
Research challenges:
Abstract repository interface
Develop API between mod_dav_repos and repository
wrappers
Scalability
Ensuring the architecture supports large numbers of
documents and storage
Supports efficient searching
Cross-repository searching
Support for efficient DASL searches
Accommodating server-defined and client-defined properties
Allowing searches that span the contents of multiple
repositories
Access Control Implementation
Create an open reference implementation of the access
control protocol
Develop an access control client that can adapt to multiple
access privilege hierarchies

36. 38
Advanced Document Collaboration
Infrastructure (4)
Work performed so far:
Created mod_dav_dasl prototype
Single database, MySQL
Storage and searching of arbitrary dead properties
Implemented DASL
Some performance characterization
Client support for DASL in cadaver client
Work is underway to release the code
Work performed by Elias Sinderson (also working
at ARC), Sung Kim, Kai Pan

37. 39
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
Work performed by Dorrit Gordon, Leila Naslavsky

38. 40
Electronic Records Management
(2)
Work performed so far:
Preliminary XML metadata schema for 5015.2 metadata
items
Modular approach allows work to potentially be used for
ERM in other countries (e.g., VERS standard in Australia)
Initial work on identifying items with controlled vocabularies
Containment data modeling of 5015.2 data model
Payoff
Wide deployment of interoperable, low-cost
infrastructure for archiving electronic records
Infrastructure for personal records management
In the future, how will you manage that 10TB hard drive on
your PC?

39. 41
Personal Digital Library
Researchers interact with a number of institutional
digital libraries
ACM and IEEE are significant for CS researchers
Limited existing support for users interacting with
these institutional DLs
Either read files online, or
Store files in a filesystem
Institutional DLs have poor track record for
reliability, QoS
 Users want to have local copies of relevant documents
Disk sizes are large, and growing
It’s reasonable to keep a copy of every document ever read
How do you manage all these documents?

40. 42
Personal Digital Library (2)
Most researchers know other researchers in their
area
If another researcher in your area finds an interesting
paper, you’ll want a copy
This should happen automatically, just by being a member
of a research peer group
Our approach:
Use a WebDAV server to store a personal, or small
workgroup’s digital library
Augment documents with bibliographic metadata
Special-purpose document browsing and searching client
Provides a document UI, not a file UI
Emphasizes bibliographic metadata in browsing UI
Integrate P2P capability for document sharing
User-selectable policies for IP enforcement
Current status: NSF proposal in-progress

41. 43
Adaptive Configuration
Management Client
DeltaV specification defines multiple packages
(feature sets) of functionality
Core versioning
Basic server workspace
Basic client workspace
Advanced server workspace
Advanced client workspace
A server may support one or more of these
Research challenge:
Create a DeltaV client that can adapt to any server it
encounters
Implies it can adapt to different workspace semantics,
and different supported features
Existing CM clients are tailored to a single system
Status: looking for a sponsor

42. 44
Software Engineering
at UC Santa Cruz

43. 45
Software Engineering @ UCSC
Currently in the process of building up an SE
research group
Hiring for three SE faculty this year
In-process of developing a Masters degree
program in Software Engineering
Aimed at working professionals in Silicon Valley
Goal is to eventually offer many courses at the UC Silicon
Valley Center (on the Ames campus)
Coursework in Software Engineering plus a significant
multi-quarter (perhaps including summer) project
Also developing a Masters program in Web and
Internet Engineering
Courses in SE, databases, networking, storage systems
Also aimed at SV working professionals

44. 48
WebDAV Resources

45. 49
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.

46. 50
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.
RFC 3253 – DeltaV Protocol
http://www.webdav.org/deltav/protocol/rfc3253.html
Extensions to the WebDAV protocol (RFC 2518) for versioning
and configuration management
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. 51
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.
J. F. Reschke, S. Reddy, J. Davis, A. Babich, “WebDAV
Search”
http://greenbytes.de/tech/webdav/draft-reschke-webdav-
search-latest.html
The most recently edited DASL protocol specification.
Significantly increased momentum recently
Likely to see specification approved this year.

48. 52
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-07, November, 2001.
http://www.webdav.org/acl/protocol/draft-ietf-webdav-
acl-07.htm
The most recent revision of the access control protocol
specification.

49. 53
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.

50. 54
Document Roadmap
Distributed Authoring
Locking, Properties, Copy/Move
RFC 2518 complete
Versioning & CM
Protocol just sent to IESG
RFC 3253 complete
Advanced Collections
Requirements and protocol for
bindings, redirectors, ordered coll.
Finish:June 2003
Access Control
Protocol for remote access control
Finish: Spring 2002
WebDAV Working Group:
DASL:
Searching
Requirements and protocol for
searching a WebDAV repository
Finish: late 2002
Delta-V Working Group:

51. 55

52. 56
Overwrite Prevention:
Locking

53. 57
Write Lock
A write lock prevents a principal without
the lock from successfully modifying the
state of the resource
Specifically, it prevents execution of PUT, POST,
DELETE, MKCOL, PROPPATCH, MOVE, LOCK,
UNLOCK
GET, PROPFIND are unaffected by write lock

54. 58
Write Lock Scope
The scope of a lock is an entire resource
It is not possible to specify a sub-resource lock.
Why?
The ability to create a sub-resource lock requires
knowledge about the content type being locked.
WebDAV wanted to support all content types equally,
not give preferential support to a few.
Due to the large number of content types, support for
sub-resource locks would have added a lot of extra
semantics to the protocol. Some content types wouldn’t
have been supported.
Content types change rapidly (two revisions of HTML and
XML occurred during development of WebDAV protocol).
Supporting one revision of a content type would make
protocol brittle, quickly obsolete.
New content types would not be supported, yet new
content types emerge constantly.

55. 59
Write Lock Scope (3)
Implications of whole-resource
locking:
Pro:
Supports existing applications which operate
on entire files, providing easy migration path
to add WebDAV support
Handles all content types
Con:
Reduced availability of resources during
collaboration (but, shared locks can help…)

56. 60
Write Lock (cont’d)
Live properties may still change even
though a lock is active
Dead properties may only be changed by
the lock owner.
A null resource may be locked to reserve its
name. This puts the resource into a special
state, lock-null, since it now has lock related
properties defined on it.
In retrospect, a bad idea
Adds a lot of special case code
Not a compelling feature for clients
Feature may go away in next revision of RFC 2518

57. 61
Lifecycle of a Lock
unlocked
locked
LOCK
UNLOCK
LOCK
(refresh)
lock timeout
administrator removal of lock

58. 62
Exclusive Lock
Zero or one possible lock holders
lock holder
access permission holders
everyone on the Internet

59. 63
Shared Lock
Zero, one, or many possible lock holders
lock holders
access permission holders
everyone on the Internet

60. 64
Why Exclusive and Shared?
Exclusive locks are too rigid
people often forget to release locks
requires an administrator to release the lock
Shared locks allow people to use out-of-band
communication to negotiate access to the
resource
if someone forgets to release a lock, it doesn’t
hold up the entire group
Collaborators work opportunistically

61. 65
Lock Compatibility
Current lock state
Shared
Lock
Exclusive
Lock
None
Shared Lock
Exclusive Lock
true
true
true
false
false false*
Legend: True = lock MAY be granted * = owner of lock MAY
False = lock MUST NOT be granted have lock regranted
Lock request

62. 66
LOCK Required Support
A WEBDAV server is not required to
support locking
Why? Systems differ markedly in the type
of locking support they provide, and may
not be able to support locks at all (i.e.,
some replicated stores)
… However, most WebDAV servers do
support locking

63. 67
LOCK Method
LOCK creates the lock specified by the
<lockinfo> XML element (in the request
body) on the Request-URI.
Lock owner information is submitted with
a lock request
A timeout value may also be requested
LOCK returns a lock token which uniquely
identifies the lock to the server

64. 68
Lock Owner Information
The owner XML element (inside <lockinfo>)
provides a means to associate lock holder
contact information with a lock.
If you want the lock holder to release the lock,
perhaps you can contact them and ask them to
relinquish it
Authentication information often does not
contain contact information (e.g., a key)

65. 69
LOCK, single resource
LOCK /webdav.html HTTP/1.1
Host: sandbox.xerox.com
Timeout: Second-500, Infinite
Content-Type: text/xml
Content-Length: 151
<?xml version="1.0" ?>
<d:lockinfo xmlns:d="DAV:">
<d:locktype><d:write/></d:locktype>
<d:lockscope><d:exclusive/></d:lockscope>
<d:owner>
<d:href>mailto:[email protected]</d:href>
</d:owner>
</d:lockinfo>

66. 70
LOCK, single resource (2)
HTTP/1.1 200 OK
Date: Tue, 09 Feb 1999 02:25:21 GMT
Server: PyDAV 1.1 filestore 1.1
Content-Type: text/xml
Content-Length: 435
<?xml version="1.0"?>
<A:prop xmlns:A="DAV:">
<A:lockdiscovery>
<A:activelock>
<A:lockscope>
<A:exclusive/>
</A:lockscope>

67. 71
LOCK, single resource (3)
<A:locktype>
<A:write/>
</A:locktype>
<A:depth>Infinity</A:depth>
<A:owner><A:href>mailto:[email protected]</A:href>
</A:owner>
<A:timeout>Second-500</A:timeout>
<A:locktoken>
<A:href>opaquelocktoken:918527121.406</A:href>
</A:locktoken>
</A:activelock>
</A:lockdiscovery>
</A:prop>

68. 72
Hierarchy Locks
Using the Depth header set to Infinity, can lock a
collection hierarchy
A single lock token is returned, identifying the lock on all
resources.
An UNLOCK on this token removes the lock from all
associated resources.
All or nothing semantics
All resources in hierarchy are locked, or none are
Hierarchy locks act to ensure:
All resources in the hierarchy are members of the lock
Resources removed from the hierarchy are removed from
the lock
But…
If a locked hierarchy is copied/moved, the destination
hierarchy is not locked.

69. 73
UNLOCK
UNLOCK removes the lock identified by a
lock token from the Request-URI, and all
other resources included in the lock
If a lock affects an entire collection, UNLOCK
removes the lock from all resources in the
collection.