The problem is that there's always a valid textual projection for any graph, but there isn't always a valid graphical projection for any text. Think like: your

The problem is that there's always a valid textual projection for any graph, but there isn't always a valid graphical projection for any text. Think like: your syntax highlighter has no idea what your code when you're in the middle of typing, because once you type an opening parenthesis without yet having typed a closing one, your code no longer has any possible valid parse. Ideally, you shouldn't be able to modify the text in ways that don't represent an atomic graphical operation in the first place. But if you enforce that, you can't really say that the textual representation is the canonical one. It's just a storage projection.