Representation of Two-Dimensional Chemical Structures

The representation of the chemical structure used by the chemist as input to and output from the chemical information system is frequently different from the internal representations of the structure used by the system. Usually chemists expect to use structural diagrams or, perhaps, the traditional linear notation. 

A connection table can be regarded as a graph, a mathematical construct that describes a set of objects, called nodes, and the relationships, called edges, between pairs of objects. In a connection table the atoms and bonds correspond to the nodes and edges of a graph, respectively. Such molecular graphs may 

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