Modeling of information systems is typically based on conceptual (intensional) primitives abstracted from a Universe of Discourse. Among different relationships the hierarchical is-a and part-of relationships play a central role in modeling. Traditionally these are viewed as separated structures. However, there are approaches that aim to view them thorough one intensional containment relationship among concepts. In this paper, we seek a solution for this philosophically hard question. In other words, we aim to find one universal relationship at the intensional level that covers both the is-a and part-of relationships. The study is based on the integration of two established theory – Kauppi's concept theory that is an intensional theory and Mereology that is a theory of parts and wholes at the extensional level.