Biochemical ontologies aim to capture and represent biochemical entities and the relations that exist between them in an accurate manner. A fundamental starting point is biochemical identity, but our current approach for generating identifiers is haphazard and consequently integrating data is error-prone. I will discuss plausible structure-based strategies for biochemical identity whether it be at molecular level or some part thereof (e.g. residues, collection of residues, atoms, collection of atoms, functional groups) such that identifiers may be generated in an automatic and curator/database independent manner. With structure-based identifiers in hand, we will be in a position to more accurately capture context-specific biochemical knowledge, such as how a set of residues in a binding site are involved in a chemical reaction including the fact that a key nitrogen atom must first be de-protonated. Thus, our current representation of biochemical knowledge may improve such that manual and automatic methods of bio-curation are substantially more accurate.