I haven't understand the concept of multiplicity properly, infact this example has confused me, Patient(0..1)<>-----kidney(1..2),how's this possible.If there is no patient,how can there be one or two kidney,can someone clarify the concept of multiplicity.Thanks in advance.
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You are reading it the wrong way around.
(0..1) is how many patients can belong to a kidney. A kidney can be inside a person, or it can be sitting outside of the patient in a surgery dish. So (0..1) makes sense.
(1..2) is how many kidneys can belong to a patient. This is kind of self explanatory. We usually have two kidneys, but we can also live with one kidney. Actually the cardinality should be more like (0..2), because you also have people that have no kidneys and live on dialysis machines.
The cardinality is a concept that is related to the relationship only.
Oliver Watkins
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