2.4. But Is It Art?

I cannot claim that the beauty of this interface was immediately obvious to me. I'm not sure it was obvious to Jim either; he was probably just trying to get Ben and me out of his house. But he'd been pondering the problem for a long time, too, and he followed his instincts about how tree structures behave.

The first thing that strikes one about the delta editor is that it chooses constraint: even though there is no philosophical requirement that tree edits be done in depth-first order (or indeed in any order at all), the interface enforces depth-firstness anyway, by means of the baton relationships. This makes the interface's usage and behavior more predictable.