The Development of Versions 3 and 4 of the Cambridge Structural Database System.

The Cambridge Structural Database (CSD) records bibliographic, 2D chemical, and 3D structural results for organocarbon compounds studied by X-ray and neutron diffraction. In January 1991, the CSD contained 86 026 entries derived from 584 primary sources. The CSD system comprises the database, together with associated software for search, retrieval, analysis, and display of the stored information. Over the past few years, the CSD system has been considerably upgraded to provide efficient, integrated, and user-friendly search facilities. The development of two new systems, Version 3 and Version 4 are described here. Both systems operate from a completely restructured CSD search file (ASER) upgraded to include bit-screen heuristics (Version 3), and further upgraded by a complete set of fully digitized 2D chemical diagram representations of database entries (Version 4). A new program, QUEST, provides integrated search facilities for text, numeric, and 2D chemical information; 2D chemical similarity searching is also included. The alphanumeric query language of Version 3 QUEST is replaced by a fully interactive menu-driven graphical interface in Version 4 in which high-quality 2D chemical diagrams form part of standard system output. Subsequent 3D search and data analysis operations are performed by the program GSTAT, common to both new systems; 3D graphical output is generated by the PLUTO package. A "general" entry-sequential search file permits both versions to operate on a wide variety of hardware platforms with minimal installation problems. Special implementations have also been developed for DEC-VAX/VMS and Silicon Graphics (Unix) environments, to take advantage of more efficient, machine-specific search file organizations. Plans for a further database upgrade and for the integration of extended 3D search capabilities into QUEST (Version 5) are briefly discussed.