editors and schemas

This might interest the document-centric folks here:

ProseMirror: A toolkit for building rich-text editors on the Web
http://prosemirror.net/

In particular, the sections describing ProseMirror's schemas and 
transformations might seem familiar, but not very familiar:

http://prosemirror.net/docs/guide/#schema

The warning, which again reminds me of XML, is:

"As such, this is more of a lego set than a matchbox car."

I suspect that folks who have built editors before will find this more 
familiar than those who work with documents in other contexts.  I 
suspect everyone will find something new, though.

Thanks,

Simon