  Although various visual interfaces for digital libraries have been developed
in prototypical systems, very few of these visual approaches have been
integrated into today's digital libraries. In this position paper we argue that
this is most likely due to the fact that the evaluation results of most visual
systems lack comparability. There is no fix standard on how to evaluate visual
interactive user interfaces. Therefore it is not possible to identify which
approach is more suitable for a certain context. We feel that the comparability
of evaluation results could be improved by building a common evaluation setup
consisting of a reference system, based on a standardized corpus with fixed
tasks and a panel for possible participants.
