Emerging Technology Briefs: WebDAV
March 26, 2002
Emerging Technology Briefs, developed by O'Reilly Research, offer a single-page summary of recent developments in a technology topic that we have been following. O'Reilly Research also publishes full-length industry reports, including the 2001 P2P Networking Overview and the upcoming Web Services Report.
|WHAT|| WebDAV (Web-based Distributed Authoring and Versioning, also called
DAV) is a set of extensions to HTTP/1.1 (HyperText Transfer Protocol, the protocol
spoken by Web browsers and servers) allowing you to edit documents on a remote Web
server. DAV provides support for:
WebDAV is platform independent, both in terms of client and server. This means that Macintosh, *nix, and Windows users can collaborate on Web content without all the usual conversion problems. Furthermore, it doesn't matter whether your documents are hosted on an Apache or Microsoft IIS server.
WebDAV is software agnostic. As long as your Web authoring tools are DAV compliant, it makes little difference which particular product you're using.
WebDAV is (at least, should be) seamless. Because DAV is simply a set of extensions to HTTP, it's easy for companies to build support into any product that already "understands" the Web. And since DAV rides on top of HTTP, firewalls tend not to get in the way of accessing your Web content remotely.
WebDAV makes use of the standard authorization and authentication methods built right into every Web Server. In the same manner as one restricts access to a portion (whether a file, folder, or entire site) of one's Web site to a particular set of users or machines, so too can one finely tune WebDAV access to resources.
WebDAV is an open standard, published by the IETF (the Internet Engineering Task Force) (RFC 2518). A completely open process, all it takes to join the working group is subscription to and participation on a mailing list.
Involved in the original development of WebDAV were representatives of companies the likes of Microsoft, Netscape, Novell, and Xerox. WebDAV support appears in a veritable cornucopia of Open Source projects, programming languages, commercial products, and services. WebDAV is baked right into the Windows (Web Folders) and Mac OS X operating systems as folders, that for all intents and purposes appear to be on your local machine, but are actually network connections to a remote server. The Zope Open Source content management system affords editing of content from well-known authoring tools like Adobe GoLive 5. DAV modules exist for most programming languages; they are either native or there are plug-ins for about every Web server in existence.
WebDAV piggybacks on the ubiquity of HTTP as the standard protocol for accessing remote resources, reaping all the benefits this has to offer: interoperability, firewall traversal, tool support, and so forth. "DAV is completing the original vision of the Web as a writable, collaborative medium. ... HTTP gave them read access, while DAV gives them write access." [WebDAV.org]
WebDAV simply extends the semantics of HTTP. It accomplishes this by adding verbs to HTTP's standard GET (e.g., GET / fetches a site's homepage for viewing in your browser) and POST (e.g., POST /form.cgi sends data from a Web-based feedback form to a CGI script). Some of these include: DELETE, which deletes a resource; PROPFIND and PROPPATCH, which respectively read and write metadata for a resource; MKCOL, which creates a new collection (you can think of these as folders collecting together files on your desktop); COPY and MOVE, which copies or moves a resource; and LOCK and UNLOCK, which set the writability of a resource to allow concurrent editing.
First proposed (albeit not submitted as a standard) in 1996, the current version, RFC 2518 was published in February 1999. Extensions to WebDAV -- such as Advanced Collections, Versioning and Configuration Managment, and Access Control -- are currently under development by the IETF WebDAV Working Group.
WebDAV continues to show up in products, projects, and services.
Oddly enough, WebDAV is not often spoken of. Perhaps this is due to it just silently working in the background and not needing much tending. Possibly it's never seemed sexy enough to demand much hype. Nevertheless, we continue to be impressed by the places WebDAV shows up -- baked right into popular operating systems (Mac OS X, Windows), well-integrated into authoring tools and content management systems for collaborative content editing and management, and available for just about every programming environment.