Query Reformulation

Users could reformulate queries in four possible ways:

• by adding ``suggested'' thesaurus terms which partly matched the initial query (after having seen the first set of search results),
• by adding terms found during thesaurus navigation,
• by adding their own terms during the session,
• by deleting terms, e.g. those added to the query by the system following relevance feedback and incremental query expansion.

Table 4a shows the total number and percentage of reformulated queries, together with the number and percentages of queries reformulated in each way. INSPEC users made heavier use of all the strategies; very few users at either site opted for thesaurus navigation.

As may be evident from the above table, some queries involved more than one kind of reformulation. Table 4b shows to what extent addition of users' own terms was combined with addition of thesaurus terms (either from the ``suggested'' list or following navigation). In practice there appears to be relatively little overlap between the two strategies.