There is a lot of discussion these days about the Web moving from being document-based to application based. Here is a section from Jeremy Keith’s book Bulletproof Ajax which talks about this:
In discussions about the difference between Web sites and Web applications, you’ll often hear about how the Web seems to be in a state of transition. It appears to be moving from a document-delivery platform to an application-based system. But this is a disingenuous distinction; it implies that applications aren’t centered on documents.
In fact, documents are at the heart of applications as well as Web sites. A work processor is useless without a document. A spreadsheet application requires a spreadsheet. Even a complex desktop application like Adobe Photoshop works on documents; the documents just happen to be images.
The difference between Web sites and Web applications lie in how malleable a document is. A traditional Web site simply displays a document. A Web application lets you interact with — and change — that document. But make no mistake: the World Wide Web is based on documents, no matter how interactive they become.