(Microsoft officials aren't commenting on anything to do with Cortana.)
Cortana, which is Microsoft's rival to Apple's Siri and Google Now, takes its codename from Cortana, an artifically intelligent character in Microsoft's Halo series who can learn and adapt. Cortana, Microsoft's assistant technology, likewise will be able to learn and adapt, relying on machine-learning technology and the "Satori" knowledge repository powering Bing.
Cortana will be an opt-in, not required, feature of Windows Phone 8.1. According to the new video, Cortana, unsurprisingly, will require users to sign in with a Microsoft Account to use the service. Once users have signed in, pressing the Bing search button will bring up Cortana as the default search engine on the phone.
Cortana initially ask users questions including their preferred nickname/name, prefered leisure activities and interaction styles and the like, according to the video. It will prompt users with sample questions and tasks they can ask Cortana to perform, such as "wake me at 7 a.m."
Cortana is core to the makeover of the entire "shell" -- the core services and experience -- of future versions of Windows Phone, Windows and the Xbox One operating systems, from what I've heard from my contacts. Cortana will debut as part of Windows Phone 8.1, which is expected to be released to manufacturing in late March or early April. It's not clear (yet) when Microsoft will add Cortana support to its other Windows platforms.