Object relationship and association in ooad concepts

Types of relationships in UML modeling

object relationship and association in ooad concepts

UML specification categorizes association as semantic relationship. Some other "Aggregation type, navigability, and end ownership are orthogonal concepts. These are the building blocks of object oriented programming and very basic stuff . Bu. Association is a relationship between two objects. In other words, association . I learnt the concept very well to be applied in OOAD. In object-oriented programming, association defines a relationship between classes of objects that allows one object instance to cause another to perform an .

Encapsulation and Data Hiding Encapsulation Encapsulation is the process of binding both attributes and methods together within a class.

  • Association (object-oriented programming)
  • Relationship types
  • UML Association

Through encapsulation, the internal details of a class can be hidden from outside. It permits the elements of the class to be accessed from outside only through the interface provided by the class.

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Data Hiding Typically, a class is designed such that its data attributes can be accessed only by its class methods and insulated from direct outside access. It should instead be accessed through the methods setValues and getValues.

Message Passing Any application requires a number of objects interacting in a harmonious manner. Objects in a system may communicate with each other using message passing. Suppose a system has two objects: The object obj1 sends a message to object obj2, if obj1 wants obj2 to execute one of its methods.

Message passing enables all interactions between objects. Message passing essentially involves invoking class methods.

object relationship and association in ooad concepts

Objects in different processes can be involved in message passing. Inheritance Inheritance is the mechanism that permits new classes to be created out of existing classes by extending and refining its capabilities. The subclass can inherit or derive the attributes and methods of the super-class es provided that the super-class allows so. Besides, the subclass may add its own attributes and methods and may modify any of the super-class methods.

Humans, cats, dogs, and cows all have the distinct characteristics of mammals. In addition, each has its own particular characteristics.

Association (object-oriented programming) - Wikipedia

The following figure depicts the examples of different types of inheritance. Polymorphism Polymorphism is originally a Greek word that means the ability to take multiple forms.

In object-oriented paradigm, polymorphism implies using operations in different ways, depending upon the instance they are operating upon. Polymorphism allows objects with different internal structures to have a common external interface. Polymorphism is particularly effective while implementing inheritance. Message passing essentially involves invoking class methods. Objects in different processes can be involved in message passing.

object relationship and association in ooad concepts

Inheritance Inheritance is the mechanism that permits new classes to be created out of existing classes by extending and refining its capabilities. The subclass can inherit or derive the attributes and methods of the super-class es provided that the super-class allows so. Besides, the subclass may add its own attributes and methods and may modify any of the super-class methods.

Humans, cats, dogs, and cows all have the distinct characteristics of mammals. In addition, each has its own particular characteristics. The following figure depicts the examples of different types of inheritance.

object relationship and association in ooad concepts

Polymorphism Polymorphism is originally a Greek word that means the ability to take multiple forms. In object-oriented paradigm, polymorphism implies using operations in different ways, depending upon the instance they are operating upon.

Polymorphism allows objects with different internal structures to have a common external interface.

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Polymorphism is particularly effective while implementing inheritance. Example Let us consider two classes, Circle and Square, each with a method findArea. Though the name and purpose of the methods in the classes are same, the internal implementation, i.

When an object of class Circle invokes its findArea method, the operation finds the area of the circle without any conflict with the findArea method of the Square class.

Generalization and Specialization Generalization and specialization represent a hierarchy of relationships between classes, where subclasses inherit from super-classes. Generalization In the generalization process, the common characteristics of classes are combined to form a class in a higher level of hierarchy, i. Specialization Specialization is the reverse process of generalization.

association in c++ - OOPS

Here, the distinguishing features of groups of objects are used to form specialized classes from existing classes.

It can be said that the subclasses are the specialized versions of the super-class. The following figure shows an example of generalization and specialization. Links and Association Link A link represents a connection through which an object collaborates with other objects. Through a link, one object may invoke the methods or navigate through another object. A link depicts the relationship between two or more objects. Association Association is a group of links having common structure and common behavior.

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Association depicts the relationship between objects of one or more classes. A link can be defined as an instance of an association. Degree of an Association Degree of an association denotes the number of classes involved in a connection. Degree may be unary, binary, or ternary. A unary relationship connects objects of the same class. A binary relationship connects objects of two classes. A ternary relationship connects objects of three or more classes. Cardinality Ratios of Associations Cardinality of a binary association denotes the number of instances participating in an association.

object relationship and association in ooad concepts

Aggregation or Composition Aggregation or composition is a relationship among classes by which a class can be made up of any combination of objects of other classes. It allows objects to be placed directly within the body of other classes. An aggregate object is an object that is composed of one or more other objects.

Benefits of Object Model Now that we have gone through the core concepts pertaining to object orientation, it would be worthwhile to note the advantages that this model has to offer. It is easy to maintain. Suppose a module develops an error, then a programmer can fix that particular module, while the other parts of the software are still up and running.

It supports relatively hassle-free upgrades. It enables reuse of objects, designs, and functions. It reduces development risks, particularly in integration of complex systems. The dot notation must be applied at the level of complete associations or higher, so that the absence of the dot signifies ownership by the association. In other words, in binary associations the dot will be omitted only for the ends which are not owned by a classifier.

Attribute notation can be used for an association end owned by a class, because an association end owned by a class is also an attribute. This notation may be used in conjunction with the line arrow notation to make it perfectly clear that the attribute is also an association end. Association end qb is an attribute of SearchService class and is owned by the class. Navigability End property of association is navigable from the opposite end s of association if instances of the classifier at this end of the link can be accessed efficiently at runtime from instances at the other ends of the link.

UML specification does not dictate how efficient this access should be or any specific mechanism to achieve the efficiency.

It is implementation specific.

object relationship and association in ooad concepts

When end property of association is marked as not navigable, in [UML 2. An end property of association that is owned by an end class, or that is a navigable owned end of the association indicates that the association is navigable from the opposite ends; otherwise, the association is not navigable from the opposite ends.

This definition is odd because it makes navigability strongly dependent on ownership, while these are assumed to be orthogonal concepts; some examples in UML 2. A2 has unspecified navigability while B2 is navigable from A2. A3 is not navigable from B3 while B3 has unspecified navigability. A4 is not navigable from B4 while B4 is navigable from A4. A5 is navigable from B5 and B5 is navigable from A5. A6 is not navigable from B6 and B6 is not navigable from A6.