Function points analysis

1. Process & Project Metrics
1. Metrics In Process & Project
Improvement

2. Software Measurement
1. Size Oriented Metrics
2. Function Oriented Metrics
3. Attributes Of Effective Software Metrics
4. Reconciling LOC & FP Metrics
5. OO Metrics

3. • Software Measurement –
- is an ability
- To measure attributes of - software & software development
process
- So that the SE activities can be improved
• s/w measurement can be classified into two categories –
1. Direct Measure
- Measures –
- cost & effort applied
- LOC produced
- Execution speed & defects
2. Indirect Measure
- measures
- functionality, quality, reliability, efficiency, maintainability,
complexity.

4. Function Oriented Metrics
• Functionalities, provided by the software is
measured
• Independent of programming language used

5. benefits of Function Points
• Function points are useful −
• In measuring the size of the solution instead of the size of the problem.
• As requirements are the only thing needed for function points count.
• As it is independent of technology.
• As it is independent of programming languages.
• In estimating testing projects.
• In estimating overall project costs, schedule and effort.
• In contract negotiations as it provides a method of easier communication
with business groups.
• As it quantifies and assigns a value to the actual uses, interfaces, and
purposes of the functions in the software.
• In creating ratios with other metrics such as hours, cost, headcount,
duration, and other application metrics.

6. How To Calculate Function Points?
• Data for following – characteristics are collected.
• Number Of User Inputs –
- each user input,
- which provides, Distinct application data,
- to the software
- Is counted
• Number Of User Outputs -
- each user output
- that provides – application data to the user – is
counted.
- ex. Screens, reports, error messages

7. • Number Of User Inquiries
- an online input
- that results in
- the generation of some
- immediate software response
- in the form of an output
• Number Of Files
- each logical master file
- i.e. a logical grouping of data, that may be part of a database
or a separate file
• Number Of External Interfaces
- all machine readable interfaces
- That are used to transmit information
- To another system
- Are counted

8. • The organization needs to develop criteria
- Which determine
- Whether a particular entry is
- simple, average or complex
• The weighting factors
- should be determined
- by observations or by experiments

9. ILF
User
Other
applications
EIF
System
Outputs
Inputs
The FPA functional units are shown in figure given below:
User
Inquiries
ILF: Internal logical files
EIF: External interfaces
Fig. : FPAs functional units System

10. Counting function points
Functional Units Weighting factors
Low Average High
External Inputs (EI) 3 4 6
External Output (EO) 4 5 7
External Inquiries (EQ) 3 4 6
External logical files (ILF) 7 10 15
External Interface files (EIF) 5 7 10
Table 1 : Functional units with weighting factors

11. Table 2: UFP calculation table
Functional
Units
Count
Complexit
y
Complexit
y
Totals
Functional
Unit Totals
Externa
l Inputs
(EIs)
Low x 3
Average x 4
=
=
High x 6 =
Externa
l
Outputs
(EOs)
Low x 4
Average x 5
=
=
High x 7 =
External
Inquirie
s (EQs)
Low x 3
Average x 4
=
=
High x 6 =
External
logical
Files (ILFs)
Low x 7
Average x 10
High x 15
=
=
=
External
Interface
Files (EIFs)
Low x 5
Average x 7
=
=
High x 10 =
Total Unadjusted Function Point Count

12. The weighting factors
- are identified for
- all functional units and
- multiplied with the functional units
accordingly.
The procedure for the calculation of
Unadjusted Function Point (UFP)
is given in table shown above.

13. Domain Characteristics Count
Weighting Factor
Count
low avg high
Number Of User Inputs * 3 4 6
Number Of User Outputs
* 4 5 7
Number Of User Enquiries
* 3 4 6
Number Of Files
* 7 10 15
Number Of External
Interfaces * 5 7 10
Count Total

14. • The Count Total – can be computed with the help of
above given table
• Now – The Software Complexity –
- can be computed
- by answering following questions
• These are complexity adjustment values – (sum(Fi))

15. 1. Does the system need – reliable backup & recovery?
2. Are – data communications – required?
3. Are there – distributed processing functions?
4. Is – performance of the system – critical?
5. Will the system – run in an existing, heavily utilized operational
environment?
6. Does the system require – online data entry?
7. Does – the online data entry – require – the input transaction to
be built over multiple screens or operations?

16. 8. Are the master files updated online?
9. Are – the inputs, outputs, files or inquiries – complex?
10. Is the internal processing complex?
11. Is the code, which is designed – being reusable?
12. Are conversion & installation included in the design?
13. Is the system designed for multiple installations in different
organizations?
14. Is the application designed to facilitate – change & ease of use – by
the user?

17. Table 3 : Computing function points.
2 3 5
4
Rate each factor on a scale of 0 to 5.
No
Influence
Average
Incidental Moderate Significant Essential
Number of factors considered ( Fi )
1. Does the system require reliable backup and recovery ?
2. Is data communication required ?
3. Are there distributed processing functions ?
4. Is performance critical ?
5. Will the system run in an existing heavily utilized operational environment ?
6. Does the system require on line data entry ?
7. Does the on line data entry require the input transaction to be built over multiple screens or operations ?
8. Are the master files updated on line ?
9. Is the inputs, outputs, files, or inquiries complex ?
10. Is the internal processing complex ?
11. Is the code designed to be reusable ?
12. Are conversion and installation included in the design ?
13. Is the system designed for multiple installations in different organizations ?
14. Is the application designed to facilitate change and ease of use by the user ?

18. • Rate –
- each of the above factors
- according to the following scale of (0 to 5)
• Function Points (FP) =
• count total * (0.65 + (0.01 * sum (Fi)))

19. 0 1 2 3 4 5

20. • Rate each factor on a scale of 0 to 5.
0 – No Influence
1 - Incidental
2 - Moderate
3 - Average
4 - Significant
5 – Essential
• Number of factors considered ( Fi )

21. • These metrics are controversial
• and are not universally acceptable.
• There are standards issued by
• the International Functions Point User Group (IFPUG)
• and
• The United Kingdom Function Point User Group
(UFPGU).
• An ISO standard for function point method is also being
developed.

22. Example:1
Consider a project with the following functional units:
Number of user inputs
Number of user outputs
Number of user enquiries
Number of user files
Number of external
interfaces
= 50
= 40
= 35
= 06
= 04
Assume all complexity adjustment factors and weighting factors are
average.
Compute the function points for the project.

23. Domain Characteristics Count Weighting Factor Count
Simple Average Complex
Number Of User Inputs 50 * 4 200
Number Of User Outputs 40 * 5 200
Number Of User Enquiries 35 * 4 140
Number Of Files 06 * 10 60
Number Of External
Interfaces
04 * 7 28
Count Total 628

24. Solution
5 3
UFP  ∑∑Zij wij
i1 J1
UFP = (50 * 4) + (40 * 5) + (35 * 4) + (6 * 10) + (4 * 7)
= 200 + 200 + 140 + 60 + 28 = 628
CAF = (0.65 + 0.01 * ΣFi)
= (0.65 + 0.01 * (14 * 3))
= (0.65 + 0.01 * 42)
= (0.65 + 0.42)
= 1.07
FP = UFP * CAF
= 628 * 1.07 = 672
We know

25. • Function Points (FP) =
• count total * (0.65 + (0.01 * sum (Fi)))
• FP = 628 * (0.65 + 0.01 * (14*3))
= 628 * (0.65 + 0.42)
= 628 * (1.07)
= 671.96

26. • Functions points may compute the following important metrics:
• Avg productivity is  6.5 FP per person-month
• (i.e. 1 person works for 1 month – to develop 6.5 FP)
• Avg labor cost is  Rs. 6000/- per month
1. Cost per function point = 6000/6.5 = Rs. 923 per function point
2. Total estimated project cost = Rs. 923 * 672 FP = Rs. 6,20,256/-
3. Total estimated effort = (672 / 6.5) = 103 person – month.
i.e. 103 person will work for 1 month to complete the project.
Or 52 person will work for 2 months to complete the project.
Or 26 person will work for 4 months to complete the project.
Or 13 person will work for 8 months to complete the project.

27. What is Person-month?
• It's mean amount of work performed by the average
worker in one month.
• So, if:
• project requires 12 persons-months of development
time
• then:
• for 12 persons-months project -
• 4 developers will spend 3 months.

28. Example:2
An application has the following:
10 low external inputs,
12 high external outputs,
20 low internal logical files,
15 high external interface files,
12 average external inquiries,
and a value of complexity adjustment factor of 1.10.
What are the unadjusted and adjusted function point counts ?

29. FP
= (10 * 3) + (12 * 7) + (20 * 7) + (15 * 10) + (12 * 4)
= 30 + 84 +140 + 150 + 48
= 452
= UFP x CAF
= 452 x 1.10 = 497.2.
5 3
i1 J1
UFP  ∑∑Zij wij
Solution
Unadjusted function point counts may be calculated using
as:

30. Example: 3
Consider a project with the following parameters.
(i) External Inputs:
(a) 10 with low complexity (b)15 with
average complexity
(c)17 with high complexity
(ii) External Outputs:
(a) 6 with low complexity (b)13 with
high complexity
(iii) External Inquiries:
(a) 3 with low complexity
(b) 4 with average complexity
(c) 2 high complexity

31. (iv) Internal logical files:
• (a)2 with average complexity
(b)1 with high complexity
(v) External Interface files:
• (a)9 with low complexity
• In addition to above, system requires
i. Significant data communication
ii. Performance is very critical
iii.Designed code may be moderately reusable
iv. System is not designed for multiple installation in different
organizations.
• Other complexity adjustment factors are treated as average. Compute
the function points for the project.

32. Solution: Unadjusted function points may be counted using table 2
Functional
Units
Count Complexity Complexit
y
Totals
Functional
Unit Totals
Externa
l
Inputs
10
15
Low x 3
Average x 4
=
=
30
60
(EIs) 17 High x 6 = 102 192
Externa
l
Outputs
(EOs)
6
0
13
Low x 4
Average x 5
High x 7
=
=
=
24
0
91 115
External
Inquirie
s (EQs)
3
4
2
Low x 3
Average x 4
High x 6
=
=
=
9
16
12 37
Externa
l
logical
0
2
Low x 7
Average x 10
=
=
0
20
Files (ILFs) 1 High x 15 = 15 35
External
Interface
Files (EIFs)
9
0
0
Low x 5
Average x 7
High x 10
=
=
=
45
0
0 45
Total Unadjusted Function Point Count 424
Software Engineering (3rd ed.), By K.K Aggarwal & Yogesh Singh, Copyright © New Age International
Publishers, 2007

33. 14
∑Fi 3+4+3+5+3+3+3+3+3+3+2+3+0+3=41
i1
CAF = (0.65 + 0.01 x ΣFi)
= (0.65 + 0.01 x 41)
= 1.06
FP = UFP x CAF
= 424 x 1.06
= 449.44
Hence FP = 449

34. Relative Cost of Software Phases

35. Example 4

36. • An application has the following:
• 10 low external inputs, 12 high external outputs, 20 low
• internal logical files, 15 high external interface files, 12
• average external inquiries, and a value of complexity
• adjustment factor of 1.10.
• What are the unadjusted and adjusted function point
counts ?

37. • Example –
• Study of requirement specification for ABC project has
produced following results –
• need for
- 7 inputs,
- 10 outputs,
- 6 inquiries,
- 17 files &
- 4 external interfaces.
• Input & external interface FP attributes are of Average
Complexity &
• all other FP attributes are of – Low Complexity
• Determine – adjusted FPs assuming Complexity
Adjustment Value is  32

38. Domain Characteristics Count Weighting Factor Count
Simple Average Complex
Number Of User Inputs 7 X 4 28
Number Of User Outputs 10 X 4 40
Number Of User Enquiries 6 X 3 18
Number Of Files 17 X 7 119
Number Of External
Interfaces
4 X 7 28
Count Total 233

39. • FP = Count Total * {(0.65 + 0.01) * Sum(Fi)}
= 233 * {(0.65 + 0.01) * 32}
= 233 * 0.97
= 226.01
Hence, adjusted FP = 226.01