Matter Substance Hierarchy

[g-guenther]

First, congratulations to this quite comprehensive material ontology - it is a very nice approach!

Second, could you explain why you don't arrange AmorphousMaterial and CrystallineMaterial (maybe together with a new class PolycrystallineMaterial) in some class (e.g. StructuredMaterial) as they exclude each other?

Third, why do you make OrdinaryMatter and Substance separate classes instead of making Substance an exact synonym for OrdinaryMatter? Wouldn't that simplify things?

Fourth, did you consider to place your nice ontology somewhere into the BFO top level hierarchy to be more interoperable with other ontologies?