The Online Search Process 

The process of online searching of remote database in most cases involves a dialogue between the searcher and the host computer on which a range of databases are mounted. A computer terminal operated by the searcher is connected to the host computer by means of a telecommunication link. An outline of the equipment is shown in the figure.    

The link between the user terminal and the host computer is often via a packet switched network. 

The flow of data is in one direction, from the keyboard to host (requests), and, in the other from host to visual display screen (information). In this dialogue, the host computer imposes constraints on what the searcher can do and when. For example, commands must be constructed in exactly the required format and often it is necessary to wait for a reply from the host before entering the next command even though the content of the command may not be dependent on the answer to the previous command.