Every process in the whiteboard marker's lifecycle has a number of inputs (material, resources and energy) and outputs (products and emissions to air, water and land). "Exchanges" is a common term for inputs and outputs and covers everything which is coming into a process and out of a process; everything which is exchanged with its surroundings.

Exchange diagram of a process

Terminal and non-terminal exchanges

Some materials and compounds in a process are exchanged directly with the environment. These exchanges are called terminal exchanges and include resource use, emissions to air, water and land (waste). In the process diagram, the terminal exchanges are illustrated with a curve. The non-terminal exchanges, such as products from another process are illustrated with a rectangular box:  

	Example of terminal exchanges from coal or oil based power production		Example of non-terminal exchanges from a whiteboard marker