Omitting information is useful for excluding unwanted detail,which might be distracting otherwise. Note that the class of physical attributes is either defined by a set of objects that constitute the class or by the object hierarchy. Figure 6.3 shows an example where everything except living beings are omitted. Highlighting information is another way for focusing the user's attention on special details. Highlighting makes it easier to spot and keep track of the selected information.
Transformation means replacing objects through other objects defined by a filter rule.
Replacing allows users to adapt whole stories to new contexts. For example, classical stories could be placed into the twentieth century by replacing horses with cars, candles with electric light, and washboards with washing machines 6.1 . Representation actions are actions which change the representation of objects in some way. For example, a blind person might want to change all visual representations to aural ones. Here is an example which illustrates the combination of these actions.