The most granular concepts we encounter are those of chemical compounds and chemical reactions, mapped as Molecule and Chemical Equation. We select a set of immutable properties that define their identity so that we can treat them as value objects. In the case of Molecule entities, we use an attribute derived from the molecular structure like SMILES or the InChiKey strings. If we formalize chemical reactions as chemical compounds that have a role (reactants, products, reagents), the set of Molecule entities and a reaction role map suffice to define the nature of a Chemical Equation. As value objects, Molecule and Chemical Equation instances constitute the nodes of a graph representation of the reaction network. The SynGraph (synthetic graph) is the central data object in LinChemIn. It contains Chemical Equations and Molecules alongside their relationships. Relevant scientific concepts map onto particular SynGraph sub-types, as shown in Figure . For instance, we define the synthetic route as a set of unique (mutually exclusive) chemical reaction steps that, arranged into a (possibly branched) sequence, are necessary and sufficient (collectively exhaustive) to assemble a target compound from starting material. We distinguish the synthetic route from simple synthetic pathways, connecting the target compound to a starting material through a linear sequence. In addition, we envision aggregative data models such as the synthetic tree (collection of synthetic routes) and the synthetic forest (collection of synthetic trees), which are necessary to collect and compare routes from different sources (CASP, NOC, etc.) for one or more targets.