Extended Function Point (EFP) Metrics

Function Point (FP) measure was inadequate for many engineering and embedded systems. To overcome this, A number of extensions to the basic function point measure have been proposed. These are as follows:

Feature Points:


• Feature Points are computed by counting the information domain values.
• It can be used in those areas where there is a level of complexity, is comparatively very high.
• Function point (FP) measure is the subset for the Feature point.
• But both the Function point and feature point represents the functionality of the systems

Table for feature point calculation:

Sr. No.	Measurement Parameter	Count	**	Weighting factor
1	Number of external inputs(EI)	–	*	4
2	Number of external outputs(EO)	–	*	5
3	Number of external Inquiries(EQ)	–	*	4
4	Number of internal files (ILF)	–	*	7
5	Number of external interfaces(EIF)	–	*	7
6	Algorithms used Count total	–	*	3

3D function points:

• Data, Functional, and control are three dimensions represented by 3D function points.
  1. Data: User interfaces and data as in the original method.
  2. Control: Real-time behavior(s)
  3. Function: Internal processing
• Data dimension calculation is the same as the FPs. Feature-Transformation is done in the functional dimension. While in the control dimension, feature-Transition is added.
• The 3D Function Point method was proposed by Boeing.
• It is designed to solve two problems with the Albrecht approach.

Example:
Compute the FP, feature point and 3D-function point value for an embedded system with the following characteristics:

1. Internal data structures = 8
2. No. of user inputs = 32
3. No. of user outputs = 60
4. No. of user inquiries = 24
5. No. of external interfaces = 2
6. No. of transformation = 23
7. No. of transition = 32 

Assume complexity of the above counts is average case = 3.

Explanation:

Step-1: We draw the Table first for computing FPs.

Sr. No.	Measurement Parameter	Count	**	Simple Weighting factor	Average Weighting factor	Complex Weighting factor	Calculated Value
1	Number of external inputs(EI)	32	*	3	4	6	128
2	Number of external outputs(EO)	60	*	4	5	7	300
3	Number of external Inquiries(EQ)	24	*	3	4	6	96
4	Number of internal files (ILF)	8	*	7	10	15	80
5	Number of external interfaces(EIF)	2	*	5	7	10	14
6	Number of Transformation	23	*				23
7	Number of Transition	32	*				32
	Count – Total			—–>			673

Step-2: Find the sum of all fi (1 to 14)

Σ(&fi) = 14 * 3 = 42 

Step-3: Calculate the functional point:

FP = Count-total * [0.65 + 0.01 *Σ(&fi) ]
= 618 * [0.65 + 0.01 * 42]
= 618 * [0.65 + 0.42]
= 618 * 1.07 
= 661.26 

Step-4: Calculate the Feature point:

= (32 *4 + 60 * 5 + 24 * 4 + 80 +14) * 1.07 + {12 * 15 *1.07} 
= 853.86 

Step-5: Calculate the 3D function point, it is calculated by counting the total calculated values. So, for 3D function points, the required index is 673.