To posterity:
I spent a lot of time in thinking about 'symbol' and what it means. Is it a fundamental concept that can exist outside of human experience, or is it an artifact that only makes sense to the human brain, specifically, the visual cortex? From the ShapeCode investigation, I think I have got an answer that satisfied me.
In case you wonder, VTracer is in fact a by-product of a side-quest which happened to be really useful. It's the pre-processor of the symbolic recognition pipeline.
The next thing I am interested in, which is equally fascinating, is 'scribble', aka hand writing recognition. If you are interested in building the next open-source hand writing recognition engine from scratch together, may be we can have a chat.
What is Semantic Computer Vision
-Chris