The data model implemented in LinChemIn (SynGraph) maps the first ontological 25 layer of reaction networks (CASP output and NOCs) to directed graphs where REACTANT and PRODUCT relationships connect Molecule and Chemical Equation nodes. LinChemIn allows the user to set the level of structural sensitivity while assigning unique identifiers to nodes by selecting among an extensible range of structure-derived molecular hashes 28 such as the Canonical 29 SMILES 30 (capturing all structural information), non-isomeric Canonical SMILES (ignoring stereoisomeric information), standard and non-standard InChIKey (ignoring tautomeric 33 information). Chemical Equation hash codes derive from Molecule hash codes through a simple combination logic inspired by the Reaction InChI 34 and extended to other molecular hashes. Using a structure-derived molecular hash as a unique node identifier is a convenient expedient to control node and graph structural equality.