The real challenge here is that document and application tend to get mixed up on the web. Looking at even a good old-fashioned blog, there are really three nes

The real challenge here is that document and application tend to get mixed up on the web. Looking at even a good old-fashioned blog, there are really three nested things on your screen: the blog post document, the blog post-viewing application, and the browser. Why a blog post-viewing application? In theory you could skip it and just have a plain reader view, but in practice you do want to have navigation and comments, and that's what the application part is for. Many modern systems surface that split in the form of an API: the API is what gives you access to the underlying document. The challenge would be making that solid accessible to the user. For example, could a browser natively have two address bars? One for the document, and one for the application that is used to access the document?