The Collaborative Web

Age : 45 Joined : 08 Mar 2008 Posts : 1850

Believe it or not, there’s more going on in Internet standards development today than just XML. To be sure, XML deserves much of the attention it’s getting, but the fanfare might be obscuring work on a number of other new foundational technologies that can also impact the future of the Net.

Near the top of that list might be WebDAV, short for World Wide Web Distributed Authoring and Versioning. WebDAV (sometimes referred to as DAV) is a set of enhancements to HTTP, the standard protocol that browsers use to communicate with servers.

HTTP provides some simple file-upload facilities, but WebDAV adds new features for making HTTP more practical as an editing platform. For example, a user editing a document stored on a WebDAV server can place a write lock on the file, protecting it from changes so that no other user can submit conflicting changes—a crucial feature for any collaborative editing environment.

WebDAV includes facilities for setting and retrieving metadata properties, such as the title or author of a document, encoded in XML form. WebDAV also lets users list, copy, move, and delete resources on the server by using URLs rather than by directly accessing the server’s file system.

The core WebDAV specification (called RFC2518) is complete and has proposed-standard status in the Internet Engineering Task Force. Work continues to extend or supplement WebDAV functionality in several areas. One initiative is the Delta-V working group, which is developing ways to manage multiple versions of documents on a WebDAV server. Another group focuses on access control, developing ways to manage user accounts and privileges remotely.

Support for WebDAV

The basic WebDAV specification is widely supported in a range of software for Web authoring and content management, including commercial and open-source software and desktop and server products. One of the most active commercial supporters of WebDAV is Microsoft, which includes support in a number of its products, including Windows 2000, Office 2000, and Internet Explorer. WebDAV is also supported in the Apache Web server through an add-on module known as “mod_dav.” The core release of the next major version of the server, the Apache 2.0, will have WebDAV support built in.

Developers say most of the available WebDAV-compliant products work together relatively smoothly. The presence of a few widely used products like mod_dav has aided interoperability by providing reference points against which other developers can test their software, says Greg Stein, lead developer for the mod_dav project.

However, some say there are still a few wrinkles to iron out. Bill Bumgarner, CFO at Web development firm CodeFab, says that though server implementations are relatively solid, desktop WebDAV clients aren’t yet consistent enough in their behavior that WebDAV can be used as a replacement for FTP in large-scale deployments. Nevertheless, CodeFab uses WebDAV internally and has implemented several recent projects that used WebDAV for server-to-server operations.

Making it easier to edit Web sites and static pages is a boon to design and development teams, but WebDAV’s impact is already spilling out beyond content management. Looking at the diverse range of projects that incorporate WebDAV today offers a glimpse of how WebDAV might change the way the Internet is used.

Endeavors Technology is using lightweight servers supporting WebDAV to realize its idea of a “federated” model of group computing. Endeavors’ model relies not on a single central work-group server but on a virtual shared workspace that resides on multiple servers running on individual PCs and handheld devices.

Another project that may use Web-DAV technology is Subversion, an open-source project that aims to create a new alternative to the Concurrent Versions System (CVS) code-repository software.

The uses of WebDAV may go even further. WebDAV’s features, notably the facilities it provides for storing metadata properties, will make it useful as a general-purpose base protocol that can serve as a foundation for many kinds of Internet applications.

Alex Hopmann, lead program manager for Microsoft Exchange, says WebDAV, combined with the SOAP protocol for XML-based interapplication communication, provides functionality that will allow an application to access data and services running on servers anywhere on the Internet. That sort of capability is central to what many believe will be the next phase of business-to-business computing: closer and deeper integration between different companies’ Internet applications. Microsoft’s particular take on the idea is .NET, a long-term plan the company announced last summer.

.NET is a long way from reality, but Microsoft is already employing WebDAV to give client applications richer access to server data. Exchange 2000’s Outlook Web Access feature, for example, uses WebDAV to send structured mailbox information to the Internet Explorer browser. In older Web mail applications, if a user clicks to sort a list of messages, the client has to transmit the sort action to the server and retrieve a whole new representation of the redrawn HTML page. But because the Outlook Web Access client gets underlying mailbox information from the server—not just HTML code for the page—it can perform simple operations like displaying and sorting in the Explorer window, without constantly chattering with the server.

Flexibility

WebDAV is extremely versatile, Hopmann says. In practice, he says, Microsoft and other vendors will still have to support widely used single-purpose protocols like the IMAP mail protocol for some time. But in principle, he believes, there is little reason application-specific protocols like IMAP and FTP couldn’t be replaced completely by WebDAV-based analogues.

That could be helpful in areas like mobile computing, says Lisa Dusseault of Xythos, maker of a WebDAV-compliant file and application server. If WebDAV-based substitutes replace IMAP and FTP, a mobile device maker could support a wide range of applications without having to support a cornucopia of protocols.

First things first, though. Stein, the lead developer of the mod_dav project, says widespread WebDAV-based application development—to say nothing of a WebDAV superprotocol taking the Internet by storm—will have to wait at least until WebDAV servers are close to ubiquitous. By his estimation, that’s still at least a year away.