Types of relations between classes

[Ahmed El-Zeedy]

Is my understanding and primitive implementations correct? could you also provide few good examples?

Association
- A child can own a parent
- A child doesn't have to be owned by a parent
- A parent doesn't have to own children
// reference/pointer of independent child object is used class Parent {    Child *childPtr; public:    Parent(Child *childObj){        childPtr = &childObj;    } }
Aggregation
- A child can't own a parent
- A child doesn't have to be owned by a parent
- A parent doesn't have to own children
// same as association
Composition
- A child can't own a parent
- A child must be owned a parent
- A parent must own a child or more
// child is created with the parent and is destroyed when parent is destroyed class Parent {     Child childObj; public:     Parent(){         childObj  = new Child;     }     ~Parent(){         delete childObj;    } }
Finally, can type of relation between same classes be different in different systems or it should reflect their real world relation?