Software Effort Estimation based on Use Case Points

1
Software Effort Estimation based on Use Case
Points

• Chandrika Seenappa
• 30th March 2015
• Professor Hossein Saiedian

2
Agenda

• Introduction
• Background
• Use Case Point Estimation Method
• Case Study
• Conclusions

3
Introduction

• Estimation of cost and schedule in software
  projects is based on the prediction of size of
  the future system
• Reliable early estimates difficult to obtain
• Lack of detailed information about future system
  at early stage
• Bidding for a contract or determining whether a
  project is feasible in the terms of a
  cost-benefit analysis
• Traditional cost model
• software size as input parameter, and then apply
  a set of adjustment factors to compute an
  estimate of total effort
• Object-oriented software production
• Object points measure the size of object-oriented
  software and are derived from class, structure,
  messages and use cases

4
Background-COCOMO

• Software cost estimation models developed in the
  60s and 70s
• Used the Line of Code (LOC) or Delivered Source
  Instruction (DSI) metrics
• COCOMO model used the DSI metric
• Problem with DSI metric
• Lack of precise definition of LOC or DSI
• No reasonable methodology to estimate upfront the
  number of source code lines or instructions

5
Background-COCOMO (Cont.)

• Metrics defined for procedural, possibly
  line-oriented languages such as FORTRAN and COBOL
• Notion of LOC or DSI difficult to define
  precisely for block structured languages such as
  Pascal, C etc.

6
Background-Function Points

• Albrecht came up with the Function Point (FP)
  metrics in 1979
• FP uses five parameters
• number of inputs
• number of outputs
• number of inquiries
• number of internal logical files
• number of external logical files
• FP is based on the number of interactions and the
  size of data to be used in the end product
• Eliminated the need for lines of code or
  delivered source instructions

7
Background-Function Points (Cont.)

• Widely used because of its independence on
  development platform and environment
• Not applicable to software products developed
  using the object-oriented methodology
• Notion of internal and external logical files
  harder to identify in the object-oriented
  paradigm.
• Not applicable for software development using
  shorter development cycles
• Difficult to apply and count function points to
  such software

8
Background-Use Case Point

• Gustav Karner came up with the notion of Use Case
  Point (UCP) in 1993
• Estimates software development effort during
  early phase of software
• Major challenge- no standard format for
  describing use cases
• UCP method adjust the use case points based on a
  number of technical and environmental factors
• Technical factors are related to non-functional
  requirements on the system
• Environmental factors characterize the
  development team and its environment

9
Use Case Point Estimation Method

• UCP is measured by counting the number of actors
  and transactions included in use case model that
  defines the functional scope of the project to be
  developed
• A transaction is an event that occurs between an
  actor and the target system
• The event being performed entirely or not at all
• Use case model mainly consists of two documents,
  system or subsystem documents and use case
  documents
• System name, risk factors, system-level use case
  diagram, architecture diagram, subsystem
  descriptions, use case name, brief description,
  context diagram, preconditions, flow of events,
  post conditions, subordinate use case diagrams
  etc.

10
Use Case Point Estimation Method (Cont.)

• Main elements to calculate UCP
• System level use case diagram
• One or more use case diagrams showing all the use
  cases and actors in the system
• Flow of events
• Section for the normal path and each alternative
  path in each use case

11
Use Case Diagram and Flow of Events
Flow of Events
Use Case Diagram
12
Counting Use Case Points
13
Counting Use Case Points (Cont.)
14
Technical Factors
15
Environmental Factors
16
Example The Online Shopping System
17
UUCW and UAW Calculation

• UAW (Total No. of Simple Actors x 1)
• (Total No. Average Actors x 2) (Total No.
  Complex Actors x 3)
• UAW (1 x 1) (0 x 2) (4 x 3) 13
• UUCW (Total No. of Simple Use Cases x 5)
  (Total No. Average Use Cases x 10) (Total No.
  Complex Use Cases x 15)
• UUCW (2 x 5) (3 x 10) (4 x 15) 100

18
TCF Calculation

• TCF 0.6 (TF0.01)
• TCF 0.6 (420.01) 1.02

19
ECF Calculation

• ECF 1.4 (-0.03 EF)
• ECF 1.4 (-0.03 10.5) 1.085

20
Use Case Points

• UCP (UUCW UAW) x TCF x ECF
• UCP (100 13) x 1.02 x 1.085 125.06
• The total estimated size to develop the software
  is 125.06 Use Case Points
• For the Online Shopping System example, 28 man
  hours per use case point will be used
• Estimated Effort UCP x Hours/UCP
• Estimated Effort 125.06 x 28 3501 Hours

21
Characteristics of Projects Evaluating the Use
Case Point Method
22
Case Study

• Web based system for handling information about
  studies conducted by Software Engineering
  Department at Simula Research Laboratory
• Software Engineering Department was both client
  and researcher
• 35 Norwegian development companies volunteered
• Requirement specification tender included 3
  actors and 9 use cases
• Bid price range from 21,000 NOK to 559,500 NOK
• Effort estimation from 78-654 hours with a mean
  of 275 hours

23
Example of Use Case
24
Company Selection

• Four companies A,B,C,D developed the project
• Companies chosen based on business and research
  criteria
• Business criteria price, experience with similar
  solutions, experience with programming
  environment(Java), size of company, understanding
  of requirements
• Development teams similar in size with 1 project
  manager and 2 developers
• Java was the development language , but with
  different tools
• Communication between client and development team
  with issue tracking system Bugzero
• System developed in parallel with time frame
  between 9 to 13 weeks

25
Characteristics of Development Projects
26
Use Case Transaction and effort for Companies
27
Effort Estimation
28
Results

• Minimum development time for 9 use cases is 413
  hours
• Actual effort of four companies
• A-587 hours
• B-943 hours
• C-431 hours
• D-829 hours
• Use case point estimation closer to actual effort
  than expert estimate based on bids

29
Conclusions

• Brief overview of effort estimation using use
  case points
• Example of estimating effort using use case
  points
• Case study based on use case points

30
References

• Anda,B., Benestad H.C., Hove, S.E. (2005). A
  multiple-case study of software effort estimation
  based on use case points. 2005 International
  Symposium on Empirical Software engineering.
  IEEE.
• Kusumoto,S., Matukawa,F., Inoue,K., Hanabusa,S.,
  Maegawa,Y. (2004).Estimating effort by use case
  points methods, tools and case study. Proceeding
  of the 10th International Symposium on Software
  Metrics, pp. 292-299. IEEE.
• http//en.wikipedia.org/wiki/Use_Case_Points