Facebook Inc is testing a personal digital assistant called M within its Messenger service that can answer questions with live human help and perform tasks such as buying gifts online and booking restaurants. "M is powered by artificial intelligence that's trained and supervised by people," David Marcus, vice president of Messaging products, wrote on his Facebook page on Wednesday, August 26. Rival services like Apple Inc's Siri, Google Inc's Google Now and Microsoft Corp's Cortana rely entirely on technology to answer questions. M is a hybrid backed by a team of Facebook employees with customer service backgrounds, called M trainers, who can also make travel arrangements and appointments, Marcus wrote. Facebook has introduced several functions inside Messenger, which boasts more than 700 million users, to transform it into a standalone platform. Earlier this year, it rolled out games exclusively on Messenger and launched products for businesses to directly connect with consumers.