rate in information business has two digits. An international database exhi- 
bition and convention INFOBASE is being held annually in Frankfurt -FRG with 
half of all earthwide available 3.000 databases being represented. 
2 Structure of computerized information retrieval 
The structure of information retrieval is shown in figure 1. Essential elements 
are database, host, telecommunication link, and the user. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Database Database Database Database 
Others Chemistry Medicine ISPRS - IRS 
H 0 S T 
  
Online Retrieval 
  
  
x 
Tymnet ! Telenet Telenet ' Tymnet 
Datex P | Euronet Euronet ; Datex P 
  
f 
  
U SIER-S 
  
  
  
Figure 1 
Structure of information retrieval 
2.1 Database 
Information is stored in databases. Information can be literature documents or 
factual data. An example of factual data is information on all companies in a 
country allowing, inter alia, to retrieve all enterprises offering remote sensing 
services. Presently, there are 2.000 databases available earthwide. A database 
may have a storage capacity of up to 1oo mio words. 
The focal point of any information system is the database. Any retrieval can be 
just as good as is the database. Consequently, the staff for establishing and 
maintaining a database for a specific field should be professionals in that 
discipline. As they should analyse the relevancy of any literature document, 
they may be called Analysts. 
A database producer must dispose on hardware. In our field, a medium size com- 
puter with appropriate storage capacity is considered to be a suitable equipment. 
Analysts maintain the database. Any Analyst should dispose on a terminal to key 
in documents. All inputs are transferred weekly or monthly to the host, online 
or by mailing a magnetic disc or tape. 
Database producers license potential hosts as online vendors. Hence, a database 
may be accessible at several hosts. 
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