SBOL cannot express recursive structures

[bbartley]

Hi, this is a little bit of an edge case, but a real one I have encountered, and also one that is philosophically interesting. The use case involved recursive nesting of recombinatorial logic in a way that controlled successive cell differentiation events. I don't know if anyone has ever actually implemented such a genetic circuit, or if real examples of recursive genetic logic exist in nature, but my scientific hunch is that recursive genetic logic could be a valid and interesting engineering approach in synthetic biology. However, we can't represent a recursive structure in SBOL without breaking validation rules. It would be interesting to explore this use case in discussions about SBOL 3.