Invisible software that you don't need to download to your desktop or open a mobile app to run, that does its work behind the scenes, and that provides a useful service--that's what startup X.ai Inc. is developing, and it is an area where startups as well as large companies such as Google Inc. are working.

Dennis Mortensen, founder and chief executive of the New York startup, told Venture Capital Dispatch that the company just raised a $9.2 million Series A round led by FirstMark Capital, a New York-based venture firm, with...