The race to teach sign language to computers

USING A computer used to mean bashing away at a keyboard. Then it meant tapping on a touchscreen. Increasingly, it means simply speaking. Over 100m devices powered by Alexa, Amazon's voice assistant, rest on the world's shelves. Apple's offering, Siri, processes 25bn requests a month. By 2025 the market for such technology could be worth more than $27bn.