Microsoft has launched a new voice-activated personal digital assistant, Cortana, on Windows Phone 8.1.

Unveiled by Joe Belfiore at the Microsoft Build developers’ conference yesterday, Cortana is being billed as the “world’s first truly personal digital assistant”, inspired by the popular character from Halo who served as a AI and a personal digital assistant to Master Chief.

“Powered by Bing, Cortana is the only digital assistant that gets to know you, builds a relationship that you can trust, and gets better over time by asking questions based on your behaviour and checking in with you before she assumes you’re interested in something,” Belfiore says.

“She detects and monitors the stuff you care about, looks out for you throughout the day, and helps filter out the noise so you can focus on what matters to you.”

Cortana will launch shortly in the US first as a “beta,” and then will launch in the US, the UK and China in the second half of 2014 with other countries to follow afterwards into 2015.

“In Windows Phone 8.1, you get to Cortana by either a Live Tile on your Start screen or by pressing the search button on your device,” Belfiore adds. “This will take you to Cortana Home. To interact with Cortana, you can either speak or type – if you’re in a meeting, just type and Cortana won’t talk out loud. But if you ask her a spoken question, she’ll answer verbally and even carry on a natural conversation.

“When you interact with Cortana for the very first time, she will start learning things about you … like your name, how to pronounce it, and ask for some personal interests.

“Once she’s learned a bit about you, Cortana’s home populates with information that is curated just for you. You’ll see things like flight information she’s found from your email confirmations, weather, the latest news, and even traffic information once she learns your commute routine, such as from work and home.”

The system keeps track of the user by storing information in “Cortana’s Notebook”, which Belfiore says will enable it to be proactive.

“Cortana can also manage your phone when you don’t want to be disturbed by setting quiet hours where she will silence any notifications, in-coming calls, and texts. Cortana understands the ‘inner circle’ of people-closest-to-you, and she can let them break through at any time during quiet hours.

“And Cortana is the only digital assistant that lets you setup people reminders.”

Because Cortana is powered by Bing, some of the interests in Cortana’s Notebook will light up on when users sign in on the Web.

“We’ve also designed Cortana to be able to interact with third party apps installed on your phone,” Belfiore says. “You can ask Cortana to help you make a video call in Skype, watch a TV show in Hulu Plus, look up a news feed on
Facebook or send a tweet using the Twitter app – all of which we demoed during this morning’s keynote.

“Finally, Cortana isn’t just a dry computer returning search results. Just as she has in the game Halo, Windows Phone’s Cortana has a bit of personality. But you’ll have to talk to her yourself to see what I mean by that.”