Some people become confused with the schematic diagram but this is simply a diagram that represents the elements or the process that people have to go through in order to reach a common goal. For example, there are some things that may be usually placed in the process that you have to go through but in an internal schematic diagram, these elements will be removed because they are not part of the process that you have to go through.
Elements that will not do anything good for the process will be removed to make the whole diagram more comprehensive and doable.