SysML FAQ: What is the difference between Generalization (“white triangle”) and Part Association (“black diamond”) relationships?

A Generalization (a.k.a., Inheritance) relationship is a “kind of” or “type of” relationship between two model elements, where one model element is generalized and the other end is specialized. A Generalization relationship is drawn as a an arrow where the tail is attached to the specialized model element, and a white triangle arrowhead is attached to the generalized model element.

A Part Association relationship is a “whole-part or “composition” relationship between two model elements, where one model element is the subject component and the other end is a part of the whole component. A Part Association relationship is drawn as an arrow where the tail is attached to the part element, and a black diamond arrowhead is attached to the whole component element.

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