An Introduction to Online Retrieval

Searching online databases is effected by means of particular database languages, so-called retrieval languages. They are commands for access to database, search, display of documents and logoff Each database supplier host -has its own language. 

A host is a company, offering access via a mainframe computer to various databases, which are produced by different database producers. Well-known hosts are for example CIS, DATA-STAR, DIALOG, DIMDI, ESA-IRS, FIZ-TECHNIK, FT-PROFILE, GBI, GENIOS, JURIS, MEAD DATA CENTRAL, NEWSNET, ORBIT, QUESTEL and STN International. 

The most important commands of the retrieval language MESSENGER from the host STN are discussed in the following chapters. A summery of the most commands is given in Sect. 8.2 in tabular form. There are no database sheets included in this book, because their use is a matter of course. 

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However, the introduction of online methods of retrieving informal tion, such as CAS ONLINE [9,10] and DARC [27] (which provide convenient and rapid searching of large files with the aid of graphic input and output), will reduce the future need for nomenclatures and notations by an extent that is difficult to predict. 

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