Apple’s voice-operated assistant Siri is in more legal trouble after a Taiwanese university launched a patent infringement lawsuit against it in a Texas court. Taiwan’s National Cheng Kung University is alleging that the iPhone service infringes two voice-to-text patents granted to it in the US in 2007 and 2010. It's also looking at whether voice recognition tech from Microsoft and Google may also have infringed its patents The voice assistant technology which Apple acquired back in 2010 has already managed to embroil the firm in several legal disputes. In China, meanwhile, a Shanghai-based developer of voice assistant technology is claiming Siri infringes a patent it holds for a "type of IM chat bot system" dubbed Xiaoi Bot, which was approved back in 2006.