When acquiring domain knowledge from multiligual text, we often encountered complicated language definitions of supertypes, such as "A is B in circumstances C" or "A is B from viewpoint C". For instance, "Physical objects in ecology are polluted or non-polluted". The non-exclusive classification is often due to ISA relationships which, in fact, imply multiple views (i.e., different perspectives) on the same type and thus reflect important semantic ambiguities in the domain. Therefore, we aim at distinguishing the different views by means of a special ISA_KIND relation which is illustrated in Figure 4. In this way one can encode explicitly the fact that POLLUTED is a subtype of PHYSICAL_OBJECT from ecological perspective or, otherwise, in the domain of ecology. On the other hand, all subtypes of NATURAL_TYPES represent natural types [Sowa 92], i.e., these are mutually-exclusive types (i.e., each individual has one natural type, as opposed to many role types) and their characteristics are persistent. Therefore, the ISA_KIND relation raises interesting questions concerning the application of inheraitance and multiple inheritance only within a given perspective.