Vertical Computer Systems is suing Microsoft for patent infringement related to Microsoft's .Net framework for building Windows-based software.

Vertical filed suit on 18 April in a US District Court in Texas alleging that Microsoft has infringed on its Patent No. 6,826,744,, for a "system and method for generating websites in an arbitrary object framework”.

The patent is for Vertical's SiteFlash technology, which uses XML (Extensible Markup Language) to create a component-based structure to build and efficiently operate websites, according to the company's website. A Vertical spokesman could not be reached for comment.

The complaint says Microsoft is still wilfully infringing on the patent despite Vertical having put Microsoft on notice about it on 7 February. Vertical is asking for a jury trial.

Vertical, based in Fort Worth, Texas, describes itself as a global web services provider. It went public in 2000 but is not listed on a major stock exchange.

A Microsoft representative was not immediately available for comment.