Connection Table Structures Systems Chemical Abstracts Service

The WLN was applied to indexing the Chemical Structure Index (CSI) at the Institute for Scientific Information (ISI) [13] and the Ituiex Chemicus Registry System (ICRS) as well as the Crossbow System of Imperial Chemical Industries (ICl). With the introduction of connection tables in the Chemical Abstracts Service (CAS) in 1965 and the advent of molecular editors in the 1970s, which directly produced connection tables, the WLN lost its importance. 

BRCT = Beilstein Registry Connection Table BRN = Beilstein Registry Number CAS = Chemical Abstracts Service CNOC = Commission on the Nomenclature of Organic Chemistry CT = connection table ICRS = Index Chemicus Registry System ISI = Institute for Scientific Information RN = CAS Registry Number SCN = Structure Code Number SSSR = smallest set of smallest rings WLN = Wiswesser Line-formula Notation. 

The first solution uses some algorithm that transforms any connection table of a molecule into a unique, canonical, form. The best known of these, the Morgan algorithm, chooses the numbering based on the numbers and properties of the neighbors of each atom of the structure. It is the basis of the Chemical Abstracts System Chemical Registry Service. There is also a canonicalization scheme for the SMILES notation of a chemical structure. ... 

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