Introducing WebDav

Darshan Singh

WebDAV (Web Distributed Authoring and Versioning) or simply DAV is a protocol (RFC 2518). More specifically, it is a set of extensions to HTTP 1.1 protocol that will enable people to read and write documents over the web. WebDAV allows users to share and work with server-based documents regardless of their authoring tools, platforms or the type of web servers on which they are stored.

WebDAV (Web Distributed Authoring and Versioning) or simply DAV is a protocol (RFC 2518). More specifically, it is a set of extensions to HTTP 1.1 protocol that will enable people to read and write documents over the web. WebDAV allows users to share and work with server-based documents regardless of their authoring tools, platforms or the type of web servers on which they are stored. WebDAV works behind the scenes over the HTTP protocol, giving users a single, consistent way to access and write documents residing on remote servers from multiple vendors. WebDAV makes the web a collaborative, -write-able- medium. By -extension of the HTTP 1.1 protocol-, I mean WebDAV adds new HTTP headers and methods as well as it specifies how to use the new extensions, how to format request and response bodies, etc.

Apart from distributed authoring, WebDAV is also targeted to provide other benefits like:

• Network file system suitable for internet: WebDAV improves navigation and manageability through documents and their properties, allowing users to navigate a WebDAV compliant server and view the server as if it was a part of local file system. WebDAV can be imagined as a remote file system with extra properties.
• Supporting remote software development teams: In the typical development cycle, source code, requirements & design documents, etc. are amenable to remote collaborative authoring, WebDAV can be used to support virtual development teams. WebDAV will also have full versioning and configuration management support, an essential collaboration component for software development.
• Common interface to a wide range of repositories, such as databases, file systems, document management, configuration management, etc.

In short, instead of passing documents back and forth via e-mail, edit them in-place at a URL!

Let’s have a look at benefits that WebDAV provides:

1. Distributed Publishing of all content to the web: Users/workgroups can now use HTTP to directly publish their work to the Web. Workgroups can collaboratively author documents in-place on the web, using locking for concurrency control, to avoid overwrite problem.
2. WebDAV has no restrictions on the type of documents which can be authored. For instance, using a DAV server, the HTML pages, images, Word documents, spreadsheets, etc, that comprise a Web site can be directly authored by the primary sources of information.
3. Managing repositories: As mentioned earlier, WebDAV makes Web look like a large-grain network-accessible file system. WebDAV provides a standard interface to manage various repositories, over HTTP.

Note that WebDAV is not a API or an application. It is a specification, a protocol, a set of extension to existing HTTP protocol.

The features-list for WebDAV include:

• Concurrency control: To avoid -lost update problem- WebDAV uses locking. The locking scheme design takes care so that to achieve robust internet-scale collaboration.
• Meta-data or Properties: Today, when the word meta-data comes along with Internet, the only technology comes into mind is XML. WebDAV uses XML for storage of arbitary meta-data (properties) about documents, which can be set, deleted, retrieved, and queried. A separate related protocol, called DASL (DAV Searching And Locating) is being developed which will provide searches based on property values to locate web resources.
• Namespace management: This feature enables users to conveniently manage Internet files and directories including the ability to copy and move files. As WebDAV works over HTTP, it has many benefits over FTP, including encryption, strong authentication, proxy support, caching, more efficient transfers (you can pipeline multiple transfers through a single TCP connection, whereas FTP requires a new connection for each file transferred.), etc.
• Version and configuration management: As with RCS, SCCS or VSS, WebDAV will also operations such as check-out/check-in, in order to store important revisions of a document for later retrieval. This feature is currently under development in the IETF.
• Access control: WebDAV will allow to set or clear access control lists, in order to limit the access rights on a given resource. This feature is currently under development in the IETF.
• Collections: WebDAV can be used to create and maintain ordered collections. For many applications, it is useful for clients to be able to impose orderings on collections at the server. When the server receives a request for a list of collection’s members, it always responds with a list ordered according to the ordering specified for that collection. For instance, for a -Product manual application- the sections of each manual may be ordered so that they can be printed together as a book. WebDAV also allows creation of symbolic link, the ability to add a referential member to a collection which can point to any resource on the Web.

WebDAV is dependent on the XML, and XML namespace standards. XML provides two major benefits to WebDAV, extensibility and internationalization. Since extra tags can be introduced with XML, WebDAV and properties can be extended easily. As XML supports multiple character sets, internationalization isn’t problem with WebDAV while storing property values which can be people from different countries.

Internet Engineering Task Force (IETF) along with Microsoft, Novell, Netscape, Xerox, University of California (Irvine), IBM, Lotus, FileNet, PCDocs, Merant, INSO, Rational, and Boston University is working on RFC 2518, WebDAV. The group is chaired by Jim Whitehead. More latest updates and news can be found at http://www.webdav.org.

Microsoft plans to incorporate support for WebDAV into the Windows 2000 operating system, Office 2000, Internet Explorer 5, IIS 5.0, etc. Microsoft shipped support for the WebDAV specification with the Beta 1 version of Office 2000 and the beta 2 version of Windows 2000. Microsoft is also providing a feature called -Web Folders- which makes a collection on a WebDAV server appear to be a directory in Windows. For more information on Web folders, have a look at knowledge base articles Q195851 (http://support.microsoft.com/support/kb/articles/q195/8/51.asp) and Q220930 (http://support.microsoft.com/support/kb/articles/q220/9/30.asp).

For more information on WebDAV projects/softwares, have a look at: http://www.webdav.org/projects.

Summary

WebDAV will dramatically reduce the accidental costs of collaboration between workgroups and between organizations. WebDAV makes the Web a simple, collaborative, writable medium. WebDAV makes web page/site creation significantly easier and also can be used to support virtual development teams.

If you have any questions/comments, feel free to use the discussion forum, or mail me – I look forward to hearing from you.