Wasn't there an effort a few years back to try to create a W3C standard for accessing data that stalled because all of the browsers used SQLite and no one wanted to create a different implementation? IIRC, the standard required two different implementations and SQLite was used by everyone?

You're think of WebSQL. My take on it dying was a combination of "key-value stores can replace relational semantics and key-value stores are cool", "only oldsters use SQL", and "wheel-reinventing is fun". The whole "we need multiple independent implementations" was a convenient excuse to kill it in my view.