The ifab-Institute of Human and Industrial Engineering at the University of Karlsruhe works in the field of ergonomic suggestive visualisation of object-oriented data within the special research centre 346 "Computer integrated design and manufacturing of parts". In general, object-oriented databases allow to represent complex object hierarchies and associations but the available tools do not use appropriately these possibilities for their visualisation. Based on already existing results and ongoing research activities for visualising data, e.g. in hypermedia and network-oriented databases, the ifab-Institute started an investigation to verify some presumptions regarding the context between object-orientation and cognition. In order to achieve the results, different methods of evaluation, ranging from simple observations of the user's actions to experimental investigations with eye mark registration were used.

The eye mark registration with a "SMI Headmounted Eyetracking Device System" was useful to trace the spots on the interface a test person was looking at, which type of information representation he or she preferred, and if the person was working according to a specific strategy of problem solving or identifying an object. The 40 test persons were all familiar with a personal computer. They all had to solve search and navigation problems in different visualisation forms of object-oriented data (e.g. list form, 2-dimensional presentation). The experimental design comprised independent variables like the colour representation, the number of objects and the number of associations between the objects.

For the development of an ergonomic suggestive visualisation of object-oriented data, it is necessary to explore the presentation of object quantities and their multiple associations. One result of the experiment is, that the search time for the objects increase linearly with the growing number of presented objects. The most effective coding changed from alphanumeric signs for 64 objects to symbols for more than 64 objects. 95% of the test persons mentioned that they prefer the presentation of associations in a list and not as graphical links between the objects on the display. This statement could only be verified for the presentation of more than 10 associations relating one object. When the interviews were compared with the results of the eye mark registration, aggravating failures in the self assessment of the test persons became evident.