Bill Stasior, the longtime former Apple executive overseeing its Siri digital assistant, has joined Microsoft, continuing a reshuffling of artificial intelligence leadership at big tech companies. Starting this month, Stasior, whose move to Microsoft hasn't been previously reported, will become a corporate vice president of technology, reporting to Chief Technology Officer Kevin Scott. Stasior referred questions about his new job to a Microsoft spokesperson, who confirmed Stasior's hiring, adding that "he will work to help align technology strategies across the company." At Microsoft, Stasior will lead an artificial intelligence group, a person familiar with the matter said. The shift underscores the intense demand for AI leadership inside the largest tech companies, all of which are jockeying for position against each other.