Siri is a virtual assistant with a voice-controlled natural language interface that uses sequential inference and contextual awareness to help perform personal tasks for iOS users. Spun out of the DARPA-funded CALO project, Siri was initially developed by Dag Kittlaus and his team of SRI International as an iPhone app. Apple bought Siri in 2010. In October of 2011 Siri was re-introduced with a new interface as part of iOS 5. Although it no longer enjoyed the same level of partner integration it had as an independent app, Apple's Siri better integration with built-in services like Messages, Mail, Calendars, Reminders, Notes, Stocks, Weather, Music, Safari, and a few external services like Google and Wolfram Alpha. It could also tie into Find my Friends.