Class Relationships, Essay Example

Introduction

Class relationship shows the connections between different models or objects that share common features. In object based modeling, class relationships are used as the major blocks of construction in modeling the different class diagrams. Class relationships are used by modelers to highlight the interaction between different objects and how the interactions affect the whole system. For example, a simple class relationship may exist in retail store where there are close relationships and interactions between stock taking and purchases within the store (Lenzerini 230).

How to express class relationships

The relationships between different classes can be expressed using the following terms, aggregation, association, composition, multiplicity and inheritance. Aggregation describes the formation of a particular class whereby the class in question results from a collection of many objects. In aggregation, the classes do not rely on each other and therefore the removal of one to the class members does not affect the other members of the class (Lano 560).

Association describes a detailed connection that exists between classes. In association one object may exist in different interrelated classes. There are different types of associations that can be used to present the connection between different objects in different classes. For instance direct association literally refers to the direct relationship between objects in a class. The other type of association is known as reflexive association which takes when an object exists in more one form within a particular class, for example a staff within an organization can either be classified as manager, an assistant manager, or a cleaner. Every form of association has roles and names (Lenzerini 230).

Composition is another element of class relationship which depends on the nature of the class. As such, when the class and its container is destroyed, composition ceases to exist. It is a relationship which tends to rely on the container of the class more than the class itself. Composition and aggregation tend to share common features; however, the main difference between the elements is that composition entirely depends on the container of the given class (Kick 270).

Multiplicity describes a relationship which entirely depends on the cardinality of the class. In this type of relationship different class may exists in a similar environment. However, the classes may share a common denominator which can be used to identify the relationship between them.

Inheritance is a form of class relationship whereby the one class emanates from a big class known as the parent. Both the parent and the child in this type of relationship share common features, however, there be some slight differences depending on the roles of each class. The child may contain specific characteristics of the parents (Kick 270).

To enhance understanding of the term class relationship, it is important to understand how different class interact and operate. The concept of realization is used in the field of modeling to understand how different classes function and interact with each other. Realization concept refers to the adoption of functions of a class that have been identified by another separate class. One class contains the functions while another class implements and uses the functions which have in turn influences the relationship and interaction between the two classes. In class modeling, broken lines can be used to indicate the concept of realization (Lano 560).

Works cited

Lano Haughton. Reasoning and refinement in oo specification languages. In ECOOP ’92. Springer Verlag, 2008.

Lenzerini Nardi, Inheritance Hierarchies in Knowledge Representation and Programming Languages. 2004.

Kick Lieberherr and Ian Holland. Assuring good style for object-oriented programs. IEEE Software, September. 2006.

Walter Opdyke. Refactoring object-oriented frameworks. Technical Report Thesis, University of Illinois at Urbana-Champain. 2006.