How are object relationships displayed by symbols?

The relationships are identified by the following symbols:

Connection occurrence in the model

Symbol for relationships for which an occurrence or an implicit connection exists in the current model.

Implicit relationship

Symbol for assignment relationships (implicit relationships).

Connection occurrence

Symbol for relationships for which no occurrences exist in the current model and that are not implicit either.

For example, if a connection was created between objects A and B and object B has been deleted, the relationship is displayed when object A is selected.