UML

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Usecase

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Association

public class Customer {
    private String name;
    private String address;
    private String contactNumber;
    }

    public class Car {
        private String modelNumber;
        private Customer owner;
   }

Agression

Paterns: <Chain of responsibility>

This shows “has a” relationship. It is a form of association relationship. This relationship highlights that a whole is made of its parts. So if a whole is destroyed the part still remains. In UML this is represented through a hollow diamond with the diamond symbol pointing towards the whole. In case of Java the aggregation follows the same structure as association. It is represented through the instance variables of a class.

public class Student {
}
public class School {
    private Student student;
}

Composition

This is again a whole or part relationship where if the whole is destroyed then the part cannot exist independently. Another important point about Composition is that the part at any point in time can have only one owner. E.g. A person can be an employee of one company at any point in time due to contractual obligations. That person cannot hold dual work authorisation. If the Company goes bankrupt the employee of this company does not exist and will be fired. The composition is represented as a filled diamond with data flowing in single direction from the whole to the part. The composition in Java is represented in the same form as aggregation with help of instance variables.

public class Employee {
}

public class Company {
    private Employee[] employee;
}

References

• Java.dzone.com, (2014). UML2 Class Diagram in Java | Javalobby. [online] Available at: http://java.dzone.com/articles/uml2-class-diagram-java [Accessed 24 Jun. 2014].

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Comparison

	Association	Aggregation	Composition
Definition	is a relationship where all objects have their own lifecycle and there is no owner.	is a specialised form of Association where all objects have their own lifecycle but there is ownership and child objects can not belong to another parent object.	is again specialised form of Aggregation and we can call this as a “death” relationship. It is a strong type of Aggregation. Child object does not have it's lifecycle and if parent object is deleted all child objects will also be deleted.
Example	Teacher and Student. Multiple students can associate with single teacher and single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. Both can create and delete independently.	Department and teacher. A single teacher can not belong to multiple departments, but if we delete the department teacher object will not be destroyed. We can think about it as a “has-a” relationship.	House and rooms. House can contain multiple rooms there is no independent life of room and any room can not belong to two different houses. If we delete the house - room will automatically be deleted. Let’s take another example relationship between Questions and options. Single questions can have multiple options and option can not belong to multiple questions. If we delete questions options will automatically be deleted.

References

• Difference between association, a. (2014). c# - Difference between association, aggregation and composition - Stack Overflow. [online] Stackoverflow.com. Available at: http://stackoverflow.com/questions/885937/difference-between-association-aggregation-and-composition [Accessed 11 Jul. 2014].

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Stereotype

allow designers to extend the vocabulary of UML in order to create new model elements, derived from existing ones, but that have specific properties that are suitable for a particular problem domain or otherwise specialized usage

<Entities>, <Boundaries>, <Controls>

Entities (model) Objects representing system data, often from the domain model.

Boundaries (view) Objects that interface with system actors (e.g. a user or external service). Windows, screens and menus are examples of boundaries that interface with users.

Controls (controller) Objects that mediate between boundaries and entities. These serve as the glue between boundary elements and entity elements, implementing the logic required to manage the various elements and their interactions. It is important to understand that you may decide to implement controllers within your design as something other than objects – many controllers are simple enough to be implemented as a method of an entity or boundary class for example.

Example

<Worker>, <Internal Worker>, <Case Worker>

Worker A Worker is a class that represents an abstraction of a human that acts within the system. A worker interacts with other workers and manipulates entities while participating in use case realizations.

Case Worker A Case Worker is a worker who interacts directly with actors outside the system

Internal Worker An Internal Worker is a worker that interacts with other workers and entities inside the system.

Entity An Entity is a class that is passive; that is, it does not initiate interactions on its own. An entity object may participate in many different use case realizations and usually outlives any single interaction. In business modeling, entities represent objects that workers access, inspect, manipulate, produce, and so on. Entity objects provide the basis for sharing among workers participating in different use case realizations.

References

• Wikipedia, (2014). Stereotype (UML). [online] Available at: http://en.wikipedia.org/wiki/Stereotype_(UML) [Accessed 16 Jul. 2014].
• Stack Overflow (2014). [online]. Available at: http://stackoverflow.com/questions/683825/in-uml-class-diagrams-what-are-boundary-classes-control-classes-and-entity-cl [Accessed 16 Jul. 2014].
• jeckle.de, (2014). UML Extensions. [online] Available at: http://www.jeckle.de/files/UML1_2/4_exten.pdf [Accessed 16 Jul. 2014].