OOP Metrics

There are many kinds of posssible OOP metrics that can be used. Here are a few that have been used (or variations of them)

 

Ave. Methods/Class   Total No. of Methods Average No. of Methods per Object Class = -------------------------- Total No. of Object Classes Value Code Reuse Extensibility Testing Comprehension higher higher worse more complicated ?

Inheritance Dependency have inheritance tree(s) Inheritance Tree Depth = max{Inheritance Tree Path Length} Value Code Reuse Extensibility Testing Comprehension higher higher than greater tree breadth ? more complicated lower

Coupling:     Degree between Objects Total No. of Arcs Average No. of Uses Dependencies per Object = ------------------- Total No. of Objects Arcs - in an Object Use-Case Maximum No. = max{No. of Uses Arcs} Arcs - attached to any single object in a use-case Value Code Reuse Extensibility Testing Comprehension higher, more coupling lower lower more complicated lower

Object Library Effectiveness Average Number of Times a Library Object is Reused: Total Number of Object Reuses Average Number = ----------------------------- Total Number of Library Objects Value Code Reuse Extensibility Testing Comprehension higher higer N/A N/A N/A

Factoring Effectiveness Number of Unique Methods Factoring Effectiveness = ------------------------ Total Number of Methodss Value Code Reuse Extensibility Testing Comprehension higher higher ? lower? N/A more reliable and easily maintained, less error in using methods

Degree of Reuse of Inheritance Methods Percent of Potential Method Uses Actually Reused (PP): Total Number of Actual Method Uses PP = ------------------------------------ x 100 Total Number of Potential Method Uses Percent of Potential Method Uses Overridden (PM): Total Number of Methods Overridden PM = ------------------------------------- x 100 Total Number of Potential Method Uses Value Code Reuse Extensibility Testing Comprehension PP higher higher N/A N/A easier PM higher higher higher N/A easier?

Application Granularity One of the goals of object-oriented design is finer granularity. The purpose is to achieve a greater level of abstraction than possible with data/procedures-oriented design. An application constructed with more finely granular objects (i.e. a lower number of functions per object) is likely to be more easily maintained because objects should be smaller and less complex. More finely granular objects should also be more reusable. ... Therefore, each object's behavior should be more easily understood and analyzed. Total Number of Objects Application Granularity = ------------------------- Total Function Points"   Value Code Reuse Extensibility Testing Comprehension higher higher higher easier higher