This page gives a few hints about Semantic techniques which can been picked while developing an extension for instance.

The Semantic Web is the extension of the World Wide Web that enables people to share content beyond the boundaries of applications and websites. It has been described in rather different ways: as a utopic vision, as a web of data, or merely as a natural paradigm shift in our daily use of the Web. Most of all, the Semantic Web has inspired and engaged many people to create innovative semantic technologies and applications. [source]

There are two examples in the Boostrap Package, that can be useful for integration in extension development:

Both are recommendation of WHATWG and W3C.