The paper reviews some of the early ideas behind the development of the theory of discrete harmonic functions. The connection to random walks is pointed out. Then a current and more general construction using weight functions is described. Discrete analogues of the Laplace operator are defined for Zn and a discrete planar hexagonal structure H. Discrete analogues of the Dirichlet problem and Po...

At the root of applications for substructure and similarity searching, reaction retrieval, synthesis planning, drug discovery, and physicochemical property prediction is the need for a machine-readable representation of a structure. Systematic nomenclature is unsuitable, and notations and fragment codes have been superseded, except in certain specific applications. Connection tables are widely ...