The MOOD metric set is used to measure the properties of the system in which the design of the system is according to the concepts of Object-Oriented Design that is Encapsulation,
Coupling, Inheritance, Information Hiding, Polymorphism.
The set contains six main metrics to measure the design of the system.
1. Method Hiding Factor(MHF) and Attribute Hiding Factor(AHF)
To measure how the attributes and methods of one class are encapsulated, Method and Attribute hiding factors are being used. MHF and AHF show the average amount of how the members of a class are hidden in the system. MHF and AHF are 100% of all the members hid, nut in the real world it is next to impossible because a class should communicate with other classes to provide different functionality of the system. It is not possible if the members are hidden Generally hiding the increase in the following order. Public, Protected Friend, Friend, Protected Friend.
If we have low MHF, then the methods are visible to almost every class. The methods are unprotected and can be subjected to changes by any class. The methods have a high tendency of reusability. In another case, if we have high MHF, then methods are not visible to many class and they can not understand the working of it. These methods can be used only by the class containing it and it has less tendency of reusability. The ideal range should be around 8% to 25%. In the case of AHF, the attributes of a class should be hidden from other classes so 100% is the ideal value of AHF. Generally, high value of AHF is advised.
2. Method Inheritance Factor (MIF) and Attribute Inheritance Factor(AIF)
In Inheritance, the child or subclass inherits the properties (Attribute and Methods) of the parent or superclass. The extent to which these methods and attributes are inherited is defined by Method Inheritance Factor(MIF) and
Attribute Inheritance Factor(AIF).
A child class that inherits a large number of methods and attributes from its parent class contains a large value of MIF and AIF. As anything in a very small amount of very high amounts is harmful, the same case is with MIF and AIF. These values should be in a reasonable range. Generally, the range of MIF is between 20% to 80% and the range of AIf is between 0% and 48%. The low value of AHF shows that class should not inherit the attributes but rather the attributes should be private to the class. The child class can make some changes (override) in the inherited methods.
3. Polymorphism Factor (PF / POF)
To measure the degree or extent of method overriding by the child class form the parent or superclass, Polymorphism Factor (PF) is used. In polymorphism, the child class can implement the method in a different way. The same method can be implemented in different ways in the child and parent class. It is defined by the ratio of an actual number of method overrides and the maximum number of total method overrides. To keep the code clean and clear and provide high quality we can use high PF but it increases the complexity of the system. Polymorphism factor is associated with method overriding, it is not associated with method overloading.
4. Coupling Factor (CF / COF)
If two or more clauses are related to each other by means of inheritance or aggregation or association then, in that case, these classes are said to be coupled. Many functionalities of the system can be done with the help of coupled classes. It is not advisable to have too many independent classes. The high value of Cf shows that the classes of the system are more inter-connected and inter-dependent. This leads to the problem that
Sometimes it is very hard to change or repair the system in case of any bugs or problem because the functionality in which the bug is, could be implemented by more than two classes and we have to make changes in all the related classes.
To measure the actual coupling between different classes Coupling Factor (CF) is used. It is the ratio of Actual coupling between different classes and maximum possible coupling can happen in the system. If a class can access the method and attributes of the second class then it is said that the first class is coupled with the second class. Generally, coupling happening due to inheritance is not considered while calculating the CF. The high value of coupling in the system leads to larger complexity. So it is advisable to have a high value of cohesion and low value of coupling. Good design architecture should contain less amount of coupling.
MOOD2 METRICS
To enhance the original MOOD metrics, the MOOD2 metrics set was later added. The new suite provides the original six metrics along with that it provides new metrics - OHEF, AHEF, IIT, PPF.
1. Operation Hiding Effectiveness Factor(OHEF) and Attribute Hiding Effectiveness Factor(AHEF)
OHEF and AHEF are better and improved versions of MHF and AHF. MHF measures the level of method hiding in the system whereas OHEF measures how good the hiding is and how well it is successfully implemented. It measures the goodness of the scope of the operation of the method of the class.
AHF measures the level of attribute hiding in the system whereas AHEF measures how the attributes are hiding and how successful the attribute hiding is. These two factors are used widely for the system that imposed the object-oriented paradigm.
2. Internal Inheritance Factor (IIF)
Internal Inheritance Factor(IIF) is the improvised version of
Method/ Attribute Inheritance Factor(MIF/AIF). To measure the internal inheritance of the software system IIF is being used. Internal inheritance means classes are inherited by the classes which are present in the given system.
3. Parametric polymorphism Factor (PPF)
It is an improvised version of the PF. It is defined as the ratio of Parametrized classes in the system to Toal no of classes in the system. A parameterized class can be considered as a generic class.
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