V Databases / Data Sources 491

491 Introduction To a large extent, chemistry is still an empirical science, building its progress on an ever increasing flood of data and information. Thus, it was realized quite early on, that this flood can only be managed by storing it in electronic form. With more than 20 million compounds known, who could know them all? And this flood constantly increases, more than one million new compounds each year, more than 500 000 publications per annum that deal in one way or other with chemical information. Chemistry was therefore one of the first scientific disciplines to start building databases to store its treasure trove of information. And, today, a effective overview of chemical information can be gained only by accessing databases. In Chapter V, Section 1 Gary Wiggins introduces us to the variety of databases available in chemistry. Bibliographic databases are described in Chapter V, Section 2 by Andreas Barth. Because chemical structures are the language of chemistry, databases of chemical structures as presented by Gregory Paris in Chapter V, Section 3 play a central role. Greg also presents an interesting overview of retrieval strategies used to gain access to the information required, a topic that is further discussed in Chapter VI. The most comprehensive chemical information system is that built by the Chemical Abstracts Service, outlined with its various components in Chapter V, Section 4 by Bill Fisanick and co-authors. The largest information system on organic compounds, which concentrates primarily on providing factual data is the Beilstein Database, described in Chapter V, Section 5 by Sandy Lawson. The various databases available in inorganic chemistry are discussed in Chapter V, Section 6 by Jürgen Vogt and Axel Schunk. Molecules are three-dimensional objects and, therefore, a knowledge of their three-dimensional structure is essential for many applications in chemistry. All small organic and organometallic molecules whose 3D structures have been determined experimentally are stored in the Cambridge Structural Database described in Chapter V, Section 7 by Frank Allen. The 3D structure of macromolecules such as proteins and nucleic acids are stored in the PDB database which is discussed, with a variety of applications, in Chapter X, Section 4.10. An enormous amount of information on chemical reactions has been stored in reaction databases – the largest of which contain several million individual reactions. These are discussed in Chapter V, Section 8 by Engelbert Zass. Spectra play a central role in structure elucidation. Despite …