Michael F. Lynch

Review of ring perception algorithms for chemical graphs

Current ring perception algorithms for use on chemical graphs concentrate on processing specific structures. In this review, the various published ring perception algorithms are classified according to the initial ring set obtained, and each algorithm or method of perception is described in detail. The final ring sets obtained are discussed in terms of their suitability for use in representing the ring systems in structurally explicit parts of generic chemical structures.

Variety generation—A reinterpretation of Shannon's mathematical theory of communication, and its implications for information science

The conventional interpretation of Shannons mathematical theory of communication in relation to textual material is unduly restrictive and unhelpful. A reinterpretation which is based on the definition of new symbol sets, comprising approximately equally-frequent strings of characters, is presented. It is shown to have wide applicability in computer-processing of texts. Moreover, it provides a more general formalism for considering methods of representing, storing and retrieving the subject content of documents.

An information-theoretic approach to text searching in direct access systems

Using direct access computer files of bibliographic information, an attempt is made to overcome one of the problems often associated with information retrieval, namely, the maintenance and use of large dictionaries, the greater part of which is used only infrequently. A novel method is presented, which maps the hyperbolic frequency distribution of text characteristics onto a rectangular distribution. This is more suited to implementation on storage devices. This method treats text as a string of characters rather than words bounded by spaces, and chooses subsets of strings such that their frequencies of occurrence are more even than those of word types. The members of this subset are then used as index keys for retrieval. The rectangular distribution of key frequencies results in a much simplified file organization and promises considerable cost advantages.

THE SHEFFIELD GENERIC STRUCTURES PROJECT : A RETROSPECTIVE REVIEW

The problems posed by the requirements for storage and manipulation of generic chemical structure definitions in patents are reviewed. Chemists and patents agents have developed an armory of linguistic devices over many decades so that a generic structure description can describe large and often unlimited numbers of substances as a result of the combinatorial opportunities provided. The nature of these linguistic devices is defined, and the theoretical foundations devised during the Sheffield project for the successful solution of the problems in order to provide the desired retrieval facilities are reviewed. Progress toward the practical implementation of a system based on these solutions is evaluated. The relevance of the data structures and algorithms devised in this work to the issues raised by developments in combinatorial libraries is also reviewed.

Automatic extraction of citations from the text of English-language patents - an example of template mining:

Methods for automatically isolating and extracting biblio graphic references from the full texts of patents are described and evaluated; these include citations both to patents and to other bibliographic sources. Patents are unusual as citing documents in that citations occur princi pally in the text of the abstracts or description parts of the documents, rather than as footnotes or in separate sections. A template mining approach has been developed for this purpose, to relieve patent examiners of the chore of doing this manually.

EXTRACTION OF INFORMATION FROM THE TEXT OF CHEMICAL PATENTS. 1. IDENTIFICATION OF SPECIFIC CHEMICAL NAMES

Much attention has been paid to translating isolated chemical names into forms such as connection tables, but less effort has been expended in identifying substance names in running text to make them available for processing. The requirement for automatic name identification becomes a more urgent priority today, not the least in light of the inherent importance of patents and the increasing complexity of newly synthesized substances and, with these, the need for error-free processing of information from patent and other documents. The elaboration of a methodology for isolating substance names in the text of English-language patents is described here, using, in part, the SGML (Standard Generalized Markup Language) of the patent text as an aid to this process. Evaluation of the procedures, which are still at an early stage of development, demonstrates that even simple methods can achieve very high degrees of success.

Theoretical aspects of ring perception and development of the extended set of smallest rings concept

This paper considers the problems associated with processing planar (two-dimensional) representations of three-dimensional structures. To overcome the ambiguity of such representations, a new ring set is defined in terms of simple faces and cut faces. The concept of a cut-vertex graph is introduced to explain the combinatorial relationship between the number of simple faces and the number of planar embedments

Text compression using variable-to fixed-length encodings

Many methods have been suggested for representing text for storage on magnetic media or for transmission down telecommunication channels with fewer bits then are required by a conventional fixed‐length character representation. These methods are reviewed, and attention is drawn to the advantages of techniques in which variable‐length character strings are represented by a fixed number of bits. Such techniques are described in more detail. The advantages and disadvantages of implementing text compression in storage and telecommunications are discussed, and an indication is given of the types of hardware which may be used. The extent to which text may be compressed with the methods discussed, and approximate timings, are stated.

Computer storage and retrieval of generic structures in chemical patents. 4. An extended connection table representation for generic structures

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Transputer implementations of chemical substructure searching algorithms

Abstract Two chemical substructure searching algorithms, the relaxation algorithm and the set reduction algorithm, are introduced and described. Transputer based serial implementations of both are compared for performance; the relaxation algorithm is shown to be both more effective and more efficient. Strategies are discussed for multi-transputer implementations of the relaxation algorithm. Experimental results show that near-linear speedups are obtained with networks containing up to 21 transputers.