Hey Guys, we’re leveraging Semantic Types for our DG project and I saw DG has these defaults for compound structures:
MOLECULE
SUBSTRUCTURE
What is the idea behind the additional SUBSTRUCTURE type?
Are there already DG features that behave differently if the SemType is set to SUBSTRUCTURE? (compared to MOLECULE)
Hi Nik, welcome! 
Substructure semantic type is meant to represent molecular patterns in the SMARTS notation. I can see that it can get confusing quickly, since most of the SMILES strings are valid SMARTS. The property editor for both is currently the same (sketcher). This semantic type is only used in a couple places (such as being a semantic type for the “pattern” parameter in the “ChemSubstructureSearch” function), and actually does not currently have any additional functionality compared to the Molecule semantic type. I would suggest to just ignore it for now; there is a chance that it will go away.