Constraint graph model properties

Chemical structures are typically represented in computer programs as bidirectional graphs used to depict a valence-bond theory model of the chemical structure. Atoms are represented by a list of nodes and bonds by a list of edges. Typically there are some constraints imposed for chemical sense (e.g., valence control), and only predefined properties can be associated with each (e.g., formal charge, bond order). Other data can be associated with the full structure (e.g., chirality, molecular formula, or any other data stored in database fields) (see Figure 1). 

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