In this example, the transformation action is currently being viewed as a type of physical transformation, which is the current role it is known to be filling. This is indicated by the function attribute of the concept, as discussed earlier (in Section 4.4.1). Notice that it would have also been possible to simply have the concept have three parent concepts--the three known roles which it could fill. The approach taken by the ISAAC system, however, is to restrict the is-a relationship to simple organization. The ability to view something as belonging to different categories is achieved through the process of considering what roles it could fill. Since this is potentially a time consuming process, this information can be cached on the concept. For example, in this concept, there are three ``known'' roles the concept may possess; these are immediately accessible. The reasoner may need to know, for instance, if the lycanthropic-transform-action is a type of magical action; the knowledge system would indicate that the concept is magical by checking the roles relationship.
Even though the lycanthropic transformation is a concept which can only exist in the story world, it can still make use of a great deal of the default information which is known about all actions. Some concepts have more default information altered in order to have them fit into the story they are used in. For instance, Figure 7 shows a partial representation for the time travel concept built after reading the story Experiment ([#!story:experiment!#]), seen in Appendix A. In the case of time travel, the standard restriction that the ending time of an action must exist after the starting time of the action (a fact known to be true about all actions in the memory of the system before any stories are read) is not always possible to maintain; therefore, that restriction has been removed from the representation.
