If you are a more functional focussed person, you are probably thinking: who cares. And if you are, please tell me why do you functional people talk so much with such a low information density? Is it thinking out loud?
Okay. Back to topic.
If you are a technical übermensch – like yours truly – you probably sh*t on people who do not see the delicate difference between a uses and an extends relationship.
In short, a tiny refresher for your brain.
- Uses (formerly known as include) indicates a “has a” relationship, and
- Extends (formerly known as extend) indicates an “is a” relationship
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As you can see I still use pre-historic diagramming. Not only because I am wise and therefore somewhat older(fashioned), but merely because I use a freely available and (almost) open source diagramming tool StarUML. This tool unfortunately stuck at UML v1.3 Notwithstanding, an excellent tool.
Translated to a real world situation:
If you are a car driver you want to drive a car. Something you must include at least once is to start the engine. An extension of driving a car is driving a formula 1 car, which indeed is something very special.
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