One of the grand challenges of Computer Science is to build a "conversational computer," or a computer that communicates with its user using a spoken interface. Apple's vision of a conversational computer was shown a few years ago, in a video called the "Knowledge Navigator."

While delivering the Knowledge Navigator remains elusive, researchers have made tremendous progress in speech and language technologies in the last decade. Speech recognition systems boast a 10-fold error rate reduction. Speech synthesis systems are approaching human-level intelligibility, in spite of their lack of naturalness. The capabilities and limitations of Natural Language Processing and Artificial Intelligence are much better understood. At Apple, we have recently integrated these technologies, and created a spoken language interface on the Macintosh called "Casper."

I will show both the Knowledge Navigator vision video, and the Casper Demonstration video. Then, I will describe the challenges and breakthroughs needed to bridge the gap between Casper and the Knowledge Navigator. Finally, I will argue that pervasive use of spoken interfaces will arrive well before the perfection of the Knowledge Navigator, and give examples of where speech technologies will be used in the next decade.