common cold u201d and then selects the select key the system returns a screen which includes a detailed description of the common cold this description is the contents of the metathesaurus entry on the common cold to further develop the query the user then selects the generalize key the system returns the screen shown in table iv to select one of these concepts the user uses the cursor to mark u201c respiration disorders u201d and then selects the select key the system returns a screen with a detailed description of respiration disorders obtained from the metathesaurus to further develop the query the user decides to make an additional entry he types in u201c melatonin u201d and then selects the add key this gives the system enough information to make a match with an available query template this however is not what the user has in mind so he uses the cursor to mark u201c melatonin u201d for further development and selects the refine key the system proceeds to display more detail about melatonin by returning on the screen of table vi a list of different types of melatonin one of these is of interest to the user and so he uses the cursor to mark both u201c respiration disorder u201d and u201c 2 phenylmelatonin u201d and selects the select key again this gives the system enough information to attempt to make a match with a query template accordingly the system searches the query templates for a possible match upon making the search the system finds a match and proceeds to instantiate the query template with the terms u201c respiration disorder u201d and u201c 2 phenylmelatonin u201d it then returns the screen of table vii this completes the formulation of the query and.