Last week, SAP and Microsoft proved what was possible when you get a couple of 16-ton gorillas to march in sync. They introduced what's for now, the enterprise's ultimate mashup: ERP and Microsoft Office. And today, SAP is making similar announcements with IBM.

Duet, the official name of the joint SAP/Microsoft offering, is designed to push SAP's installed base past the core 10 - 20% of the enterprise. The value proposition is, wouldn't it be great if a manager who needs budget rollups once or twice a week gets them fed to the Excel spreadsheets that is his/her de facto standard? Or what about the road warrior who would rather stay in Outlook than fiddle with the CRM system?

Clearly, people are more productive when they work with the software they know, and don't have to go elsewhere to cut and paste data or rely on a custom interface. And the idea of an all-in-one desktop is nothing new. It drove emergence of the first word processor/spreadsheet/calendar bundles 20 years ago, and got a shot in the arm once the Mac GUI enabled you to cut and paste data from one app to another.

But finding a way to mass-produce enterprise mashups encompassing business functionality has remained elusive.

The emergence of services-oriented architectures, which supported loosely coupled and dynamic connections, moved the integration ball off dead center. SOAs enabled SAP and Microsoft to do Duet, and for IBM to knit SAP into IBM Lotus Workplace and WebSphere Portal.

While SOA makes integration easier, it's still not easy. Duet, which is actually more of a conventional packaged product with specific functionality that you install and configure, required two years of development for its first modest HR-focused release. By contrast, IBM, which took a toolkit approach, got the offering out in only six months, but it leaves actual integration to the customer.

Either way, you can't just pick the pieces you need on the fly; either the vendor must prepackage them or you must integrate them yourself.

In large part this explains the popularity of Ajax-style mashups. That's Zimbra's approach to groupware, which seeks to unify two of the most popular enterprise apps: email and web browsing. Because Ajax focuses on rich UI rather than transaction integration, and because it uses some of the best-known web languages around, it's a pretty fast way to make enterprise mashups.