History.js gracefully supports the HTML5 History/State APIs (pushState, replaceState, onPopState) in all browsers. Including continued support for data, titles, replaceState. Supports jQuery, MooTools and Prototype.

You might have a finite set of data that you need to fetch once for your application.
You might have a feed of data that is constantly updating and thus your collection periodically check for updates.

Dealing with the first scenario is quite simple. It would require defining a Collection constructor that has a url property. Calling fetch on an instance of that collection would then fetch the data and that would be sufficient.

Dealing with the second scenario is somewhat more complex for several reasons