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Monday, April 18, 2011

What is Deployment Level Design ? What are Design Metrics?


The Deployment-level Design creates a model that shows the physical architecture of the hardware and software of the system. The Deployment Diagram is made up of nodes and communication associations. Nodes would represent the computers. The communication associations show network connectivity. To develop deployment level design, distribute the software components identified in the component-level design to the computer node where it will reside.


There are many sets of metrics for the object-oriented software. Chidamber and Kemere Metrics suite consist of six class based design metrics:
Weighted Methods per Class (WMC)
- This is computed as the summation of the complexity of all methods of a class.

Depth of the Inheritance Tree (DIT)
- It is defined as the maximum length from the root superclass to the lowest subclass.

Number of Children (NOC)
- Children of a class are the immediate subordinate of that class.
- As the number of children increases, reuse increases.
- Of course, as the number of children increases, the number of testing the children of the parent class also increases.

Coupling Between Object Classes (CBO)
- It is the number of collaboration that a class does with other object.
- As this number increases, the re-usability factor of the class decreases.

Response for a class (RFC)
- It is the number of methods that are executed in response to a message given to an object of the class.
- As this number increases, the effort required to test also increases because it increases the possible test sequence.

Lack of Cohesion in Methods (LCOM)
- It is the number of methods that access an attribute within the class.
- If this number is high, methods are coupledtogether through this attribute.

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