This is a matter of aesthetic tidiness. Figures 2-8 and 2-9 show elements of these.

·         If one side of two or three boxes are approximately in line with each other—line them up. For example, check out Laboratory Test and Observation in the two diagrams. Also Sample with both Laboratory Test and Observation.

·         If you have several sub-types in a super-type, and it is reasonable to do so, make them the same size. (Yes, there are exceptional circumstances, sometimes.) Also put reasonable space around them. In the examples, see Observation’s sub-types: Direct Observation and Physical Observation.

·         The constraints described in the previous sections will make it impossible to completely ...

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