Search ‘command mode’ was historically the first method of query input and use of logical statements together with Boolean operators and extensions (e.g. proximity operators) continue to be used in both commercial databases and library catalogues. Despite this, research (Cooper, 1988; Ensor, 1992; Harman, 1992; Larson, 1992) has demonstrated that users often have problems with Boolean operators i.e.:
- Conceptual problems with formulation
- Unranked result sets that are too large or small
- Lack of weighting of results
Because of this several improvements have made in many contemporary systems e.g.:
- Result ranking
- Weighting of terms
- Proximity operators
- Faceted navigation to deal with large result sets.
Selection from lists of terms is often combined with either templates or logical statements. It enables users to select terms from indexes, dictionaries or controlled vocabularies and include them directly in the search statement.