Microsoft plans to release two components of its next-generation Expression development suite to its Microsoft Developer Network (MSDN) subscribers, as the company seeks to generate buzz in preparation for a key conference next month.

Expression Web, a web design tool roughly comparable to Adobe’s Dreamweaver but based on Extensible Application Markup Language (XAML), is available immediately, according to a blog posting by S ‘Soma’ Somasegar, corporate vice president of Microsoft’s developer division. Expression Blend, an interactive design tool still in beta, will be released to MSDN subscribers sometime this quarter.

That could be as soon as early next month, when Microsoft holds its Mix07 developers conference in Las Vegas. At the event, the company will try to woo developers and designers over to the Expression tools, as well as cross-platform runtimes such as Windows Presentation Foundation/Everywhere (WPF/E).

Similar in concept to Sun Microsystems’s Java or Adobe’s Flash technologies, WPF/E is a small software plug-in that enables graphically rich mini-applications built with the Expression tools to run inside the web browser.

The latest community technical preview of WPF/E, which runs inside internet Explorer 6 and 7, as well as Firefox 1.5 and 2.0, was released in early February. Samples of those applications can be downloaded from Microsoft’s site.

Tim O’Brien, director of Microsoft’s platform strategy group, said that WPF/E provides many of the same offline capabilities as other development tools and platforms announced in the past month. Those include Adobe’s Apollo, Joyent’s Slingshot and even the Mozilla Foundation’s upcoming Firefox 3.0 browser, which, when released later this year, will have the ability to let users run web applications such as Google’s Gmail or Docs when they are not connected to the internet. Documents that are created or changed while offline will be synchronized smoothly back to the web service when the user is connected again.

But Microsoft hopes developers and designers will choose its platform and tools because of Expression’s underlying use of XAML code, a variant of XML. That, the company said, should help remove the traditionally clumsy hand-off between programmer and designer, speeding development time. Expression Studio, parts of which remain in beta, happen to be the only tools right now that can create applications working with the WPF/E plug-in. But O’Brien said that "any tool that can output XAML can work with WPF/E."

As for its own desktop software franchises, Microsoft remains committed to its software-plus-service mantra, which is to build online-only add-ons that complement -- but don't replace -- existing desktop applications. In practice, that means Outlook Web Access as a complement to Outlook on the desktop, or Excel web Access in SharePoint as a complement to Excel, O’Brien said.

While a number of software-as-a-service challengers to Microsoft Office’s dominance have recently signalled their intention to add more offline capabilities to their online-only offerings, O’Brien said that Microsoft is unlikely to do the same, since it already has the full desktop version.