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enter image description here

I don't know how to interpret this dot diagram (black and transparent)

What is the relationship about them?

Stephen C
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dumb163
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    [1 to many relationship](https://en.wikipedia.org/wiki/One-to-many_(data_model)). BTW, this is not Java. – Elliott Frisch Mar 27 '23 at 14:20
  • https://stackoverflow.com/questions/885937/what-is-the-difference-between-association-aggregation-and-composition – knittl Mar 27 '23 at 14:21
  • So `equipment_state_ history` have a composition of `equipment_state` and `equipment`? then `equipment_state_history` inicializator I need code like `
    private equipment equipment;
    public class equipment_state_history
    {equipment = new Equipment();}` alright?     – dumb163 Mar 27 '23 at 14:36

1 Answers1

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The black diamond indicates that those are Composition associations; i.e. a "part-of" relationship. The Classifier at the end with the diamond is the composite or "whole", and the the other end it the "part".

The grey filled circles at the other end could indicate that that end is "owned" by the Classifier at that end. But they should be black filled ... if that is what they are supposed to indicate. (And ownership is rarely indicated in UML class diagrams in practice.)

The cardinality of the composition association is not indicated directly. However the aggregation implies that the end with the diamond has multiplicity of "1..1", and we can assume that the other end will be "0..*" (or * for short). In database terms these are "one to many" relationships.

The fact that the Association is a dotted rather than solid line is (I think) non-standard. Dotted lines are officially used in UML notation for Dependencies ... but these are clearly not Dependencies. The alternative interpretation is that the dotted lines have been used by the design tool for "artistic" reasons. That could also apply to the grey filled circles. I am inclined to >this< explanation.

Stephen C
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  • Tools tend to apply their own "art" to UML rendering. Some get quite off here. The above is completely wrong with the dashed lines being used for dependencies. But the latter do not have isOwned nor the composite aggregation – qwerty_so Mar 27 '23 at 21:36