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					                              Cost Estimation



                                  SYST510



Peggy Brouse, Ph.D. SYST510
                                                1
              Software Cost Estimating
        What are we costing?
        Program code, source & executable that
         is delivered to the client together with
         appropriate documentation, training and
         other items that lead to a complete
         software system.



Peggy Brouse, Ph.D. SYST510
                                              2
                    Perspectives for Cost
                         Estimation
          Wholistic
             Examination of product as a WHOLE
             No Examination Review of Micro-Level
              Details
             Experientially Based Intuitive, Affective
          Heuristic
             Use of Rules of Thumb


Peggy Brouse, Ph.D. SYST510
                                                          3
                    Perspectives for Cost
                         Estimation
          Holistic
             Determination of Micro-Level Details
             Determination of Cost or Value of These
             Sum These to Determine Overall Costs or
              Value




Peggy Brouse, Ph.D. SYST510
                                                   4
                              Cost Models
          Definition:
             Management tools that predict life cycle
              development costs for software acquisition
              across system definition, development, and
              deployment phases




Peggy Brouse, Ph.D. SYST510
                                                     5
                              Cost Models
          Purpose:
             To encompass software system costs and
              schedule projections from requirements
              analysis phase through product
              acceptance and maintenance phases




Peggy Brouse, Ph.D. SYST510
                                                  6
                              Cost Models
          Cost Drivers:
             Number of delivered source lines of code
              (SLOC), function points, tasks




Peggy Brouse, Ph.D. SYST510
                                                     7
                 Conventional Approach
        Base an initial cost estimate on amount
         of code to be delivered. Estimate may
         be modified by complexity factors.
        Lines of Code
             High Order Language LOC
             Source LOC
             Delivered SLOC


Peggy Brouse, Ph.D. SYST510
                                              8
                              Example:
          Summary of Deliverable Source
           Instructions:
                              Modules   %     DSI

               New            19        56%   13491

               Adapted        15        44%    2005

               Total          34              15496
Peggy Brouse, Ph.D. SYST510
                                                 9
                     Difficulties with LOC:
        Complex instructions receive same
         weight as simple statements
        It is not a uniform metric in that
         machine-oriented language statements,
         higher-order language statements, &
         very-high-order language statements
         given the same weight.


Peggy Brouse, Ph.D. SYST510
                                              10
                     Difficulties with LOC:
        Programmers may artificially increase
         their productivity by writing many simple
         lines of code.
        May encourage poor-quality code by
         encouraging rapid production of sloppy
         code



Peggy Brouse, Ph.D. SYST510
                                               11
                       Model Construction
        Identify Theory of How Factors Relate
        Establish Structural Framework
             Behavioral Observations, Physical
              Observations, Hypotheses
                  Theoretical
                  Empirical




Peggy Brouse, Ph.D. SYST510
                                                  12
                       Model Construction
          Identify Unspecified Factors for Best or
           Satisfactory Replication
             Use Data and Observations to Adjust
              Unspecified Factors
          Estimate the Worth of the Model
             Based on Forecast or Prediction



Peggy Brouse, Ph.D. SYST510
                                                    13
                       Model Construction
          Model Validity
             Structural Validity
                    One to One Correspondence - Model to Actual
                     System or Process
             Parametric Validity
                  Unspecified Factors Accurately Identified
                  Close Correspondence to Actual System




Peggy Brouse, Ph.D. SYST510
                                                               14
                       Model Construction
             Forecast or Prediction Validity
                    Projects Future Events, Costs, or Schedules
                     within Acceptable Error Tolerances




Peggy Brouse, Ph.D. SYST510
                                                                   15
                       Model Construction
          Use Regression Analysis to Develop a
           Model
             Determine Candidate Factors and Data
              Collection
                  Describe Dependent Variables as a Function of
                   Independent Variables
                  Experience-based Intuition, Existing Theory or
                   Knowledge
                  Joint Observation of all Factors: not less than
                   10 times the number of Factors

Peggy Brouse, Ph.D. SYST510
                                                               16
                       Model Construction
          Postulation of Model or Structure
             Usually an Equation:
                              y=a+bx
          Choice of Estimation and Selection
           Method




Peggy Brouse, Ph.D. SYST510
                                                17
                       Model Construction
          Determine Regression Curve
             Obtain Needed Data
             Use Subportion in which Algorithms for
              Factor Estimation have been Encoded




Peggy Brouse, Ph.D. SYST510
                                                       18
                       Model Construction
          Iteration and Sensitivity Analysis
             Test to Determine if Model is Accurate
          Completeness Criteria
             All Important Explanatory Factors Taken
              into Account
             Do Results Make Sense
             Can Assertion Be Validated


Peggy Brouse, Ph.D. SYST510
                                                        19
                    Revised Intermediate
                     COCOMO (REVIC)
        Developed by Maj. Ray Kile, AF
         Reservist
        Originally based on a database of 281
         contracts involving software completed
         at RADC
        Use 19 factors to compute person
         months for a project

Peggy Brouse, Ph.D. SYST510
                                              20
                    Revised Intermediate
                     COCOMO (REVIC)
          Factors are broken into 4 groups:
             Product
             Computer
             Personnel
             Project




Peggy Brouse, Ph.D. SYST510
                                               21
                    Revised Intermediate
                     COCOMO (REVIC)

        Factors are generally given a rating
         from Very Low (VL) to Very High (VH)
        Each rating corresponds to a numerical
         value




Peggy Brouse, Ph.D. SYST510
                                             22
                    Revised Intermediate
                     COCOMO (REVIC)
        When all 19 values are multiplied
         together, an environmental factor (x) is
         created
        Person Month Estimate:
             Months= a(KDSI) * x
                 a = depends on developmental mode (organic,
                   embedded, semidetached)



Peggy Brouse, Ph.D. SYST510
                                                           23
                  Taxonomy of Factors -
          Personnel Attributes
             PCAP (Programming Team Capability)
                    NM> medium previous performance, avg.
                     educational background, avg. team
                     communication
             ACAP (Analyst Team Capability)
                    NM> medium previous performance, avg.
                     educational background, avg. team
                     communication

Peggy Brouse, Ph.D. SYST510
                                                             24
                  Taxonomy of Factors -
             AEXP (Project Application Experience)
                    NM> Design & development team's exp. on
                     projects of similar complexity of 2 to 5 years
                     relevant experience
             LEXP (Language Experience)
                    NM> experience with programming language of
                     12-17 months




Peggy Brouse, Ph.D. SYST510
                                                                      25
                  Taxonomy of Factors -
             VEXP (Designer's & Programmer's Exp.
              w/Target Host Hardware & Software)
                    NM> No use of HOL, not familiar w/host
                     machine, BUT has s/w experience




Peggy Brouse, Ph.D. SYST510
                                                              26
                  Taxonomy of Factors -
          Computer Attributes
             TIME (Execution Time)
                    NM> CPU utilization between 60 & 70%
             STOR (Additional work for software
              development due to constraints on memory
              in the target computer)
                    NM> Based on ratio of estimated storage
                     requirements to memory capacity


Peggy Brouse, Ph.D. SYST510
                                                               27
                  Taxonomy of Factors -
             VIRT (Degree of change machine is
              projected to undergo during the design &
              dev of the project)
                    NM> 1 change every 3 months expected




Peggy Brouse, Ph.D. SYST510
                                                            28
                  Taxonomy of Factors -
             TURN (Computer Turn Around Time)
                    NM> Avg. time for host or dev. computer to
                     complete an action <= 4 hours




Peggy Brouse, Ph.D. SYST510
                                                                  29
                  Taxonomy of Factors -
          Product Attributes
             RELY (Required Software Reliability)
                  NM> Moderate difficulty in recovery
                  VH> Failure could cause loss of life

             DATA (Extra effort required to create a
              project that will maintain a sizable
              database)
                    NM> Based on ratio of size of database to # of
                     DSI

Peggy Brouse, Ph.D. SYST510
                                                                30
                  Taxonomy of Factors -
             CPLX (Software Product Complexity)
                    NM> S/W has data proc. and stnd. math &
                     statistical routines




Peggy Brouse, Ph.D. SYST510
                                                               31
                  Taxonomy of Factors -
          Project Attributes
             MODP (Modern Programming Practices as
              outline by Barry Boehm: top down reqs.,
              structured design, walkthrus, structured
              code)
                    NM> Some use of MODP by exp. analysts (not
                     programmers)




Peggy Brouse, Ph.D. SYST510
                                                            32
                  Taxonomy of Factors -
             TOOL (Use of Software Tools)
                    NM> Use of Basic Mini Tools: HOL compiler,
                     macro assembler, library, database aids




Peggy Brouse, Ph.D. SYST510
                                                              33
                  Taxonomy of Factors -
             SCED (Effect that Compressing or
              Extending the Schedule will have on
              person months)
                    REVIC has the capability to set the actual
                     schedule in months which will in turn compute
                     the revised costs.




Peggy Brouse, Ph.D. SYST510
                                                                34
                  Taxonomy of Factors -
          Additional Attributes in REVIC
             SECU (Classified Security Application)
                    CL> Project is Classified
             RISK (Management Reserve for Risk)
                    VL> Very low program risk




Peggy Brouse, Ph.D. SYST510
                                                       35
                  Taxonomy of Factors -
             RUSE (Required Reusability)
                    NM> No contractually required reuse of the
                     software
             RVOL (Requirements Volatility)
                    NM> There will be small noncritical redirections




Peggy Brouse, Ph.D. SYST510
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posted:10/30/2011
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