关键词：
Chemical data
Computerization
摘要：
An evaluation is given of the search strategies used in the screening stages of the Sheffield generic structure system. The results of several searches are presented;a detailed account is given of their performance together with a discussion of outstanding problems and weaknesses. The screening stages are of two types, a fast bitscreening stage using inverted files of bitstrings and a slower but more discriminating stage which operates on files of reduced graphs. Bitscreens are used to represent the presence, absence, or possible presence of features attributable to the structure. These features are of two types: fragment descriptors and ring descriptors. The results of searches using these screening stages are encouraging. The diversity of the methodology used is reflected in the results;the strengths of each method are shown to resolve the weaknesses of others. The final stage of search, the refined search, is introduced. This is a localized atom-level search which investigates, in greater detail, the mappings between reduced graph nodes which result from the reduced graph screening stage. This is the most discriminating search stage and is therefore expected to be highly efficient.
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