A common technique used to index chemical structure information within modern (O)RDBMS systems such as Oracle and IBM DB2 is discussed.

There is focus on:
1. Subgraph isomorphism detection of (sub)structures within adjacency matrices - algorithms that must be implemented within any serious chemoinformatic COTS product such as MDL, Daylight, ChemAxon, Accelrys, InfoChem, and Cambridgesoft Oracle Data Cartridge implementations.
2. Discussion on (O)RDBMS implementation theory for extensible indexing of chemical entities, implementation architecture, and available technologies.
3. Flaws and/or simplicity of approach in many chemically aware DBMS extensible indexing implementations when dealing with, on occasion, undergraduate chemical concepts.
4. Chemoinformatic application of RDBMS theory in the 1930's.