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Reading a Generalization Hierarchy

publish date: 2026/06/08 08:10:23.773381 UTC

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The diagram below shows a UML generalization hierarchy for doctor types in the Mentcare system.

In this UML generalization hierarchy, which direction does the arrowhead point?

Upward, toward the more general superclass

There are no arrowheads — generalization uses plain lines only

Horizontally, between sibling classes at the same level

Downward, toward the more specific subclass

Correct Answer

Upward, toward the more general superclass

Explanation

In UML generalization, the arrowhead (an open triangle/hollow arrowhead) points upward toward the more general class (the superclass). This indicates that the lower-level class (subclass) is a specialization of the more general class above. For example, the arrow from Hospital Doctor points up to Doctor, indicating Hospital Doctor is a type of Doctor.

Reference

Software Engineering, Ian Sommerville, 9th edition

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Structural Models