Microsoft has released architectural guidance for organisations looking to offer software as a service (Saas) on this week.

A sample application that is designed to illustrate what Microsoft categorises as key architectural principals of Saas will be featured. "The app itself is a fictitious HR [human resources] application," said Tim O'Brien, director of the platform strategy group at Microsoft.

"The functions it provides from an HR standpoint are less interesting than the architectural principals underneath," O'Brien said.

The application is single-instance and multi-tenancy, and guidance is provided on resource sharing as it pertains to an application.

"Multi-tenancy is a real important architectural concept for companies transitioning to Saas," because scaling is required, said O'Brien. There are challenges to getting software to scale so another instance of the application is not required, he said. Also featured are rules for security to make sure data does not leak from one tenant or user to another.

The application in question uses Microsoft's C# and managed code technologies. The Visual Studio 2005 platform also is featured, as are Microsoft's SQL Server database and Internet Information Server. Microsoft is intending to show how to deal with SAAS issues using its technologies, but the intent is more to focus on implementation, O'Brien said.

"This is more of an architectural challenge," O'Brien said.

Microsoft's guidance is to be released on developer site, Microsoft Devenloper Network. And the company plans to offer its Dynamics customer relationship management (CRM) package and Office Live software in a hosted Saas format later this year.

Users are looking to Saas to either move application maintenance out of their own data centres or to try an application before buying it, said O'Brien. The future will entail users hosting applications internally and utilising Saas, he said.

An analyst noted Microsoft's belief in a hybrid model for software delivery. "This is basically Microsoft [providing] a first step in guidance down that road," said Lyn Robison, an analyst in the application platform strategies service at Burton Group.