Problems we should avoid
From HAO Wiki
Introducing unusable terms
All terms entered into the ontology are potentially usable, so we should avoid the temptation to introduce unusable terms. An example might be adding a term called 'views' to "organize" terms that refer to view angle (e.g., 'dorsal' is a 'view'). The problem is that 'views' is not really a term people use and could complicate some of the services the ontology might provide in the future.
Adding too much and potentially conflicting information
Term A is part of Term B, and Term C is a synonym of Term A. If we define those relationships we shouldn't then have to say Term C is part of Term B.

