Conceptual diagrams are derived directly from bubble diagrams. They are highly abstract and symbolic.
Concept diagrams can be done with any free flowing media, such as pencil, marker, felt pen, or coloured pencils.There are no conventional symbols that are right or wrong. However, most of the graphics at this beginning design stage are very abstract and are not meant to convey exact shapes, texture, or forms. They primarily express functions, activities, spaces, and their relationships.
Here are a few examples.