What separates enterprise apps from desktop apps? Mainly, business rules and workflow. Wednesday, at the (PDC) Professional Developers Conference, Microsoft announced Windows Workflow Foundation (WWF), a brand new Windows technology that will enable developers to stitch together Microsoft Office apps and custom-built software into composite, enterprise-class workflow applications. With WWF, according to group product manager Scott Woodgate, Microsoft will be able to offer "the first workflow-enabled operating system."

WWF is the biggest surprise in a flurry of Microsoft announcements, which kicked off this week with Bill Gates" demo of the first public beta versions of Vista and Office 12. Along with WWF, Microsoft is talking up its new Atlas Web toolkit for building AJAX (Asynchronous JavaScript and XML) applications, plus a new lighter, more portable version of XAML (Extensible Application Markup Language) dubbed XAML/E (the "E" is for "everywhere").

These introductions follow on the heels of Microsoft"s surprise distribution of its WinFS (Windows File System) beta two weeks ago. Add to that Windows Communication Foundation (Microsoft"s stack of WS-* protocols, formerly called Indigo and already in beta), and some might view all those new APIs as one big learning curve. But Tim O"Brien, Microsoft"s group manager of platform strategy, sees them as fulfilling a promise: "PDC five years ago was really around unveiling .Net. We look at today as a realization of the dream we articulated five years ago."

WWF is a key part of that dream. Many have long wondered how Microsoft would leverage its desktop dominance in an XML and Web services world. WWF will have the effect of making Office, which in version 12 will support WWF, part of a distributed app dev environment. For example, with MS"s SharePoint portal server as the front end, developers will be able to exploit Outlook for routing messages and use templates in Word, Excel, and Access to create powerful, process-driven apps.

Developers can take advantage of WWF using a GUI plug-in to Visual Studio 2005 or simply edit the underlying WWF code. Changes to the code are immediately reflected in the graphical schematic and applications can even be constructed to enable end users to change workflows. "With WWF, Microsoft will let programmers to isolate process logic and business rules as they create composite applications," says Woodbridge. Yet WWF is language-independent, using a sequencing engine to run processes. A BPEL (Business Process Execution Language) module is available now as a free download, but other orchestration schemes will be supported as well.

Perhaps the biggest shocker is that Microsoft is announcing WWF and making a beta version available the same day -- not long after releasing the WinFS beta early. For shipping versions of these and other nexgen APIs, we"ll have to wait until the second half of 2006, when Vista and Office 12 are also supposed to ship. Until then, developers can take advantage of these four technologies" backward compatibility and play with betas on Windows Server 2003 or Windows XP.