JSON-LD
Linked Data empowers people that publish and use information on the Web. It is a way to create a network of standards-based, machine-readable data across Web sites. It allows an application to start at one piece of Linked Data, and follow embedded links to other pieces of Linked Data that are hosted on different sites across the Web.
Source: JSON-LD
Interesting idea, but I have my doubts that it would take off. HTML covers too much of the same ground.