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Systems diagramming
Systems diagramming

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3.8 Reading diagrams: questioning what they say

With each of these diagrams and others we are trying to read there is another set of more searching questions we can ask:

  • What is the purpose of the diagram, i.e. what is it aiming to tell us?

  • How is the information imparted?

  • What assumptions does it make about our ability to understand it?

  • What are we expected to remember from it?

  • How successful is it in doing all of the above?

Activity 4

Look at the diagrams again and apply these questions to them. You may find this activity difficult until you have worked through more of this course but have a go now and come back to it again when you have completed the course.


My response to Figure 8

Purpose: The purpose is summed up by the caption or title (which should be a major function of the title). With no other indications we do not know if this is someone's summary notes for helping to write a paper or give a talk or what someone has produced after reading a book on the subject.

How imparted: The information is imparted in a clear manner through the use of words and interconnecting lines radiating from the original topic.

Assumptions: That these are notes, but whose notes is not clear.

Remember: That there are a lot of topics and activities relevant to a high-technology area such as mobile telephony and that these include social, legal and economic ones as well as the technological ones.

How successful: This diagram does successfully convey the message that there are many aspects to mobile telephony that need to be considered, but without knowing its purpose precisely it is hard to know how successful it has been in achieving that purpose.

My response to Figure 9

Purpose: To show that signals can take more than one path to a receiving mobile telephone and that these vary in length. The significance of this is not clear from the diagram and its caption alone and may have been mentioned in the accompanying text.

How imparted: The information is imparted through a mixture of realistic pictures and lines with arrows to indicate the paths of a mobile telephone signal.

Assumptions: That the length of the arrows is representative of the lengths of the signal's paths and that the mobile phone is being used in a moving car.

Remember: That mobile telephone signals take direct and indirect paths to the receiving phone.

Successful: This method of representation makes an immediate visual impact and gets the main message across quickly. The implicit message of the different lengths of signal path are less certain and does not say at all what the actual distances involved may be, nor the likely speed or position of the car and hence the phone.

I hope that this activity and my responses have made you think a bit harder about what diagrams are trying to communicate to you and how you can interpret them. This is not always easy. It can involve familiarity with the conventions. It can involve moving between a diagram and some associated text. It can involve changing your ideas about a situation. It may require a different approach to the one I have used here. And sometimes, as with a difficult piece of text, you have to get what you can out of a diagram even if you have not fully grasped all its nuances. The best way of learning to read diagrams is to gain experience with a wide variety of diagrams over time so that you automatically question what they ‘say’ to you.