You might, but the expansion happens on a level that might be really hard to implement if you want to keep XML semantics. E.g. in the DOM API, each element has

You might, but the expansion happens on a level that might be really hard to implement if you want to keep XML semantics. E.g. in the DOM API, each element has its own identity - you can't collapse identical objects (or you could, but the objects generated this way aren't identical, they have different parent nodes for example).