The Role-Relationship-Model : Supporting the Generic Definition of Relationships
Relationships between entities are a very important part of each conceptual model. The participation of an object in a relationship influences the behaviour of that object: It needs the ability to interact with related objects. In the classic object oriented models and languages, relationships and their semantics are hidden behind attributes and specific object methods. Instead, the Role-Relationship-Model provides an explicit relationship concept which comprises relevant methods for objects participating in the relationship. The Role-Relationship-Model is based on a role model which allows objects tho change their types during their lifetimes. By defining a relationship, the participating entity types get new subtypes which contain the methods for interacting with related objects. An object is related to another object by acquiring such a subtype. Based on this relationship concept, generic and composite relationships are introduced. By specifying a generic relationship, the operational semantics of a class of relationships is described. The generic relationship can be instantiated as a relationship between specific entities. By instantiating relationships in the context of another (generic) relationship definition, (generic) composite relationships are built which represent more complex structures and their behaviour.
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