The Generator — CONGEN

Constraints can be substructures, ring size, number of hydrogen atoms, and number of isopren substructures. The first step is to define superatoms, which constitute substructures that are handled as individual nodes in the graph. A CONGEN user can work interactively — for instance, to retrieve the existing solntions at any stage or to define fnrther constraints if the nnmber of results is too high. 

A successor of CONGEN is Generation with Overlapping Atoms (GENOA), which introdnced several improvements to functionality and interactivity [3]. GENOA allows for the overlap of substructures as well as for defining limitations for a series of possible snbstructures. It reduces the number of constraints and gives the ability to retrieve intermediate resnlts. 

CONGEN and GENOA can handle any structure and can enumerate the isomers of a molecular formula, and they are able to generate structures with more restrictive constraints (e.g., isomers with specific molecular fragments). Both GENOA and CONGEN use heuristic rather than systematic algorithms. 

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