Search

This paper reviews the use of similarity searching in chemical databases. It begins by introducing the concept of similarity searching, differentiating it from the more common substructure searching, and then discusses the current generation of fragment-based measures that are used for searching chemical structure databases. The next sections focus upon two of the principal characteristics of a similarity measure: the coefficient that is used to quantify the degree of structural resemblance between pairs of molecules and the structural representations that are used to characterize molecules that are being compared in a similarity calculation. New types of similarity measure are then compared with current approaches, and examples are given of several applications that are related to similarity searching.

The history of the development of computer systems for storage and retrieval of Markush structures is reviewed briefly. The systems currently being developed by Chemical Abstracts Service, Derwent Publications/Questel/INPI, and International Documentation Company for Chemistry (IDC) are introduced, and the similarities and differences between the approaches they use for input representation and search are examined, especially in relation to the handling of generic nomenclature, the prospects for future development of such systems is discussed in light of recent and continuing research work, as is the potential for exchange of Markush structure databases between the different search systems.

One of the problems encountered in handling computer representations of combinatorial libraries (especially “virtual libraries”) is the extremely large number of compounds which may be covered by even quite simple libraries. This paper discusses work on the generation of structure fingerprints for the compounds in a library, which avoids the need to enumerate the compounds themselves by utilizing techniques originally developed for handling Markush structures in chemical patents.

Barnard Chemical Information Ltd.'s software products for generation of fragment-dictionary-based chemical structure fingerprints and for hierarchical and nonhierarchical clustering of large files of structures are described.

This paper addresses the problems associated with chemical structure searching of the patent literature. The deficiencies of existing services are reviewed, and the results of continuing research aimed at overcoming these problems are presented. These take the form of a systematic structure description language (GENSAL) for generic structure input, a topological representation of generic structure (ECTR) suitable for ma chine processing, and algorithmic screening strategies for generic structure searching and retrieval.

Description d'un programme informatique permettant l'analyse syntaxique et semantique des structures generiques codifiees selon le langage GENSAL

Le role de ces structures dans une base de connaissances en chimie est decrit, notamment en relation avec les brevets. Les systemes d'information operationnels permettant l'acces a ces structures sont presentes