The second concept is so called functional dimensions. It was introduced by Aleksandr Bukalov. He defined the first dimension as the personal experience (Ex), the second dimension as social norms (Nr), the third dimension as the current situation (St), and the fourth dimension as the globality, or time perspective (Tm). This concept is useful because it best illustrates the difference in cognitive power (imagine measuring capability of 2D v. 3D measuring tool) and roughly describes abilities of each function to process and generate information. Still, definitions of dimensions require further research and clarification. For example, the vulnerable function tends to lose knowledge which haven't been used.