Representatives of US electronics giant Apple Inc appeared in a Shanghai court on Tuesday for an intellectual property rights case involving the software for Siri, its voice-activated digital assistant.

Siri responds to a user's commands through voice recognition software.

Shanghai Zhizhen Network Technology Co, the developer of a voice technology called Xiao i Robot, alleged that Apple's Siri had infringed the patent they hold relating to "a type of instant messaging chat robot system".

"We noticed iPhone 4S' digital assistance Siri copied Xiao i Robot's artificial intelligence technology when it came out in 2011. As a national enterprise, we have enough reason to protect our own rights,"said Zhizhen's chairman Yuan Hui.

Zhizhen had filed for a patent for its software with China's State Intellectual Property Office in 2004, and received approval in 2006, Yuan said.

According to Zhizhen's marketing department, Xiao i Robot now has 100 million users across China.

Siri Inc, essentially a start-up company Apple acquired in 2010, started producing the mobile virtual assistant in 2007. Apple later bundled the technology into their iPhone 4S smart phone in 2011.

Yuan from Zhizhen said his company had asked Apple to stop the infringement, and requested no further financial compensation.

That would mean Apple and its local subsidiary would have to stop manufacturing, selling and using products with Siri technology in any system higher than Apple IOS 6, including the iPhone 4S, iPhone 5, iPad 3, iPad 4 and iPod touch 5, said Zhizhen's attorney Yuan Yang, from DeBund Law Offices.

Apple, however, said it had already applied to the State Intellectual Property Office of China for the invalidation of Xiao i Robot's patent and that the result would come out soon.

The ruling from the State Intellectual Property Office will have a great impact on the case, according to lawyers from both sides.

"We filed for the invalidation as an immediate and normal response to being sued,"said Tao Xinliang, Apple's attorney from Dacheng Law Offices.

Si Weijiang, another lawyer representing Zhizhen, said the result from the State Intellectual Property Office would be available in August and that the court would probably wait for the ruling.

Zhizhen filed the lawsuit on June 21, 2012, only a few days after Apple paid $60 million to Proview Technology (Shenzhen) to end a protracted legal dispute over the iPad trademark in China.

This is the third time Apple has been sued in China for patent infringements. Jiangsu Xuebao Daily Chemical Co Ltd had previously alleged the Chinese translation of Mac OS X Snow Leopard infringed its trademark rights. The case is still ongoing.