Abstract

There are three conditions which an item has to fulfill in order to be listed into an inventory. Based on those three conditions, the logically basic entities are introduced: they are points, sets, and collections. These logically basic entities are related with three different logical relations, i.e., “is an element of”, “is a subset of”, and “is a part of” –relations, to constitute concepts. Those three logical relations have different relational properties, and thus they are to be distinguished. The logically basic entities are said to exist whereas the concepts constituted by them are said to subsist. One of the most important results is that we should not mix two inventories together, since otherwise inconsistencies follow.