| one-to-one composition | is a subtopic of 5.6 - More Advanced Features of Class Diagrams |  |
| is a kind of composition | |
| often corresponds to a complex attribute that can be shown as an attribute or, if you want to emphasize the details of the composed class, as a composition | |
| composition | has example The rooms of a building cannot exist without the building | |
| is drawn as a solid (filled-in) diamond in a UML diagram | |
| aggregation | represents 'part-whole' relationships | |
| association | can have a label which is an association name or a role name | |
| describes a relationship that will exist between instances at run time | |
| has default name "has" if it has neither an association name nor a role name | |
| has part association name | |
| has part role name | |
| is bi-directional unless it has an arrow at one end indicating directionality | |
| is legitimate only if its links will survive beyond the execution of any particular operation | |
| is usually implemented using instance variables in Java: you divide each two-way association into two one-way associations - so each associated class has an instance variable | |
| may be implemented in several ways in Java | |
| must not be added to a model unless it is relevant to the application - it will be needed to implement some requirement | |
| should exist if a class possesses, controls, is connected to, is related to, is a part of, has as parts, is a member of, or has as members, some class in your model | |
| should have sufficient names to make the association clear and unambiguous | |
| shows how two classes are related to each other | |
| data abstraction | groups the pieces of data that describe some entity, so that programmers can manipulate that data as a unit | |
| helps a programmer to cope with the complexity of data | |
| hides the details of data | |
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