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Scientists ask several different types of question involving chemical structures with other property data. ICI has considered these question types in developing the CROSSBOW system for chemical structure recording and search. The system relies on the use of the Wiswesser Line‐Formula Notation to represent structures as compact, logical, unique and unambiguous codes suitable for computer processing. The notations can be converted into detailed explicit descriptions of molecular structure known as connection tables. These allow the most exact atom‐by‐atom search technique for a specified atomic network anywhere in the molecule. To facilitate more general searches, and to provide a screen to reduce input to the exhaustive atom‐by‐atom procedure, two other chemical search techniques are implemented. The first is a fast search for the occurrence of certain chemical fragments, using a fragment set generated from the notations: the second is a search of the notations themselves for symbol strings relating to the required substructure. Output from the search is in the form of structural diagrams generated from the connection tables. Data from associated property files can be displayed along with the structures, or searched as an additional parameter. The CROSSBOW system operates not only on ICI internal files, but also on commercially‐available data bases. These include the Aldrich chemical catalogue, the Index Chemicus Registry System current awareness tapes, and Hansch structure/activity files.

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The rules of precedence of the Wiswesser Line Formula Notation for polycyclic structures are of such a nature that the canonical notation for complex structures is sometimes obtained only with time-consuming effort. A computer program has been written which accepts as input a set of nonconsecutive locant pairs which unambiguously describes a cyclic structure. The program operates on this information and produces a detailed analysis of the network according to the rules of the notation. The correct canonical notation is also prepared by the program. As a by-product of this analysis, the program punches on cards the nonconsecutive locant pair sets for each one of the paths tried. These data are used to accumulate an index of the structures analyzed and thus prevent

As an enthusiastic believer in the value and usefulness of vector and point analysis, I can not avoid a feeling of regret that several different systems of notation should be in use to express identical or very similar ideas. The general introduction and use of directional methods of operation must certainly be hindered by such a state of affairs. The vector system of Professor Gibbs, which is already familiar to some through the pamphlets on the subject printed by him for private distribution some years ago, agrees to some extent with that of Grassmann, though the notation and some of the fundamental ideas are different. Every relation treated in this book can be as well, and often more simply, expressed in a notation differing from that of Grassmann only in the omission of the brackets surrounding combinatory products, which seem to me unnecessary.