Comment by iainmerrick

Thinking about it, I'm not sure any interchange spec would leave useful room for innovation. This isn't like EPS or PDF or something where the kind of output is well-defined (printable graphics + text) and the innovation is in the editing interface. The innovation in canvas apps is surely in the semantics of the nodes themselves; but if you add some new node type with special behavior, how can you usefully export that to other apps? You could make it a black box that can round-trip safely, but that doesn't seem very useful. Maybe if it's something like an HTML embed or iframe?