WebDAV

What is WebDAV?

Web-based Distributed Authoring and Versioning (WebDAV) is a new Internet specification that extends the HTTP protocol.

The stated goal of the WebDAV working group is (from the charter) to "define the HTTP extensions necessary to enable distributed web authoring tools to be broadly interoperable, while supporting user needs".

Until now, the web has been mostly a read-only environment. We read pages off of the web, and occasionally sign a guest book or add a book review to somebody else's web site. While that has been enormously useful, two things have emerged:

PROPPATCH (to add properties to a resource or collection)

1) Until now, adding new pages on the web has been more complicated than it needs to be. Generally, people who don't have direct access to a server have had to understand FTP to get new pages on to the web. Many people have been able to figure out FTP, but many more have not. What's more, FTP is not a very well controlled environment, and as a result, there are many organizations that aren't comfortable offering FTP access to their servers.
2) People are looking at the Internet to supplement or replace private networks, such as LANs. People want easier ways to work from home (telecommute), or to cooperate with someone on the other side of the country, or to send data to a supplier. Thus people need to be able to share files and other resources over the Internet the same way they share files and resources on networked file systems.

WebDAV serves and HTTP Protocolas a network file system suitable for the Internet, one that works on entire files at a time, with good performance in high-latency environments. It also acts as a protocol for manipulating the contents of a document management system via the Web.

An important goal of DAV is to support virtual enterprises, being the primary protocol supporting a wide range of collaborative applications. Importantly, a major goal is the support of remote software development teams. A final goal of DAV is to leverage the success of HTTP in being a standard access layer for a wide range of storage repositories -- HTTP gave them read access, while DAV gives them write access.

Features
WebDAV provides a network protocol for creating interoperable, collaborative applications. Major features of the protocol include:
¢ Locking (concurrency control): long-duration exclusive and shared write locks prevent the overwrite problem, where two or more collaborators write to the same resource without first merging changes. To achieve robust Internet-scale collaboration, where network connections may be disconnected arbitrarily, and for scalability, since each open connection consumes server resources, the duration of DAV locks is independent of any individual network connection.
¢ Properties: XML properties provide storage for arbitrary metadata, such as a list of authors on Web resources. These properties can be efficiently set, deleted, and retrieved using the DAV protocol. DASL, the DAV Searching and Locating protocol, provides searches based on property values to locate Web resources.
¢ Namespace manipulation: Since resources may need to be copied or moved as a Web site evolves, DAV supports copy and move operations. Collections, similar to file system directories, may be created and listed.

Technical Specifications
WebDAV is an extension of the HTTP/1.1 protocol. DAV adds new HTTP methods and headers. In addition, DAV specifies how to use the new extensions, how to format request and response bodies, how existing HTTP behavior may change, etc.

WebDAV 1.0 adds seven additional methods to the HTTP protocol:

• MOVE (to move a resource from one URL to another)
• COPY (to copy a resource from one URL to another)
  
• MKCOL (to create a new collection of resources -- like a directory or folder)
  
• PROPPATCH (to add properties to a resource or collection)
  
• PROPFIND (to get properties from a resource or collection)
  
• LOCK (to lock a file so that no one else can change it while you're working on it)
  
• UNLOCK (to unlock the file)

Benefits of WebDAV
Web sites typically gather information from geographically separated people. Using a DAV server, such information that comprises a Web site can be directly authored by the primary sources of the information.

DAV provides a standard infrastructure for supporting geographically dispersed software development teams by making the software remotely accessible via the Internet. Since the artifacts of software development, like requirements and design documents, as well as source code, are open to remote collaborative authoring, DAV can be used to support virtual development teams. While DAV has significant utility today to support remote software development, when the versioning protocol has been completed, DAV will have full versioning and configuration management support as well, an important collaboration technology for software development.

PROPFIND (to get properties from a resource or collection)

• LOCK (to lock a file so that no one else can change it while you're working on it)
  
• UNLOCK (to unlock the file)

Useful Links
1) WebDAV Home Page
1) Introduction to WebDAV