Words do not provide an appropriate or adequate means of describing visual artifacts.
Users can also indicate their level of uncertainty regarding certain attributes of the query.
Copyright on this material is held by the authors. They can include photographs, drawings, paintings, slides, prints, or X-Rays. Visual databases may be interrogated for many reasons such as instruction, communication. exemplification, sourcing, problem solving. In many cases the only way in which material can be accessed is through a text based classification system, developed primarily to aid cataloguing the material, not selective retrieval. For example, a doctor might remember having seen a similar cell pattern before, but would be unable to locate this particular slide if items were stored solely by patient number.