Interactive visualization offers an alternative querying mechanism. The underlying assumption is that querying becomes a continuous exploration task. Detailed user knowledge of a query language (procedural or declarative) is no longer a prerequisite as simple graphical tasks can be used to explore the data set. As for output, the visual display is used to convey implicit information in addition to explicit query results. Specifically, through the articulation of visual mappings, users can obtain information on patterns in the data in addition to the explicit output representing the results of a query. Thus, querying becomes synonymous to exploring, investigating, discovering, learning rather than mere answering of a question.
We have recently experimented with prototypical implementations of visual query systems using conventional GUI toolkits, 2D graphic libraries and 3D toolkits (see below for some examples).