Figure 2-5 shows an example of a data model arranged randomly. Note that there are no crossing lines, but that does not prevent it from being quite difficult to understand. It appears to be about a laboratory, but that’s as far as the casual observer could be expected to go. Perhaps if the person viewing it were thoroughly versed in laboratory principles—and patient in navigating all the lines—it would be understandable. To anyone else, however, it is quite hopeless.
Figure 2-5: A Random Data Model
Figure 2-6 shows a somewhat neater version of the same model. In this case, all relationships are shown with direct, straight lines. ...