Oh! Was Murray Shanahan's lab involved with this? Cool. I've chatted with Murray a very tiny bit on twitter about this all. That paper is part of what inspired me to write this blog post, because I was dissatisfied with the approach they propose.

It felt to me like they had found a way to restrict "symbolic" data to a very narrow domain where issues like hierarchical structure was totally absent, and vectorial representation was therefore quite straight forward, and I wanted to figure out an alternative. Instead of restricting the kinds of symbolic data involved, do the full spectrum. I had the symbolic vector idea in my head for about two years as an answer to the representation problem, but I hadn't seen what the right answer was to the other aspects, at least not clearly. But that paper motivated me to start thinking about it again, and this time I saw the answer. :)