Estimation Models in Software Development
Empirical Estimation Models like COCOMO and Constructive Cost Model play a crucial role in estimating software project efforts based on various factors such as lines of code (LOC) and function points (FP). These models provide a structured approach to predict project duration, effort, and team size. The use of coefficients and regression analysis on empirical data helps in accurate estimation, aiding project planning and resource allocation.
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Structure Estimation Model COCOMO Model - Basic Model - Intermediate Model - Detailed COCOMO Model COCOMO II model - Application Composition Model - An Early Design Model - A Reuse Model - Post Architecture Model
Structure Estimation Model This model - Is derived using - Regression analysis on data - Collected from - past software projects The estimated efforts can be denoted by following formula
E = A + B * (Ev) ^ C Where, - - - ABC are constants, derived empirically E is the effort in persons-months Ev is the estimation variable, derived from LOC or FP
COnstructive COst MOdel There are 3 classes of software projects Organic Mode - small, simple projects - with small & less experienced teams are handled. Semi Detached Mode - intermediate projects - teams with mixed experience level are handled Embedded Projects - - combination of hardware, software & operational constraints
1. Basic Model Estimates, the software development effort - using only LOC Various equations in this model are E = Ab (KLOC ) ^ Bb (effort estimation) D= Cb (E) ^ Db (duration estimation) P= E/D (persons estimation)
Co-efficients of Ab, Bb,Cb,Db for three models are Software projects Organic Semi- detached embedded Ab Bb Cb Db 2.4 3.0 1.05 1.12 2.5 2.5 0.38 0.35 3.6 1.20 2.5 0.32
Example 1 Consider a software project using semi detached mode with 30000 LOC. 1. Effort Estimation E = Ab (KLOC ) ^ Bb = 3.0 (30) ^ 1.12 = 135 Person-month
2. Duration Estimation D= Cb (E) ^ Db = 2.5 (135) ^ 0.35 = 14 months 3. Persons Estimation P= E/D = 135/14 =10 persons approximately
Example 2 Using COCOMO, estimate the time required for the following 1. Semi detached model, for software project of 2000 lines 2. Embedded model of software of 30,000 lines 3. An organic model of software of 1,00,000 lines 4. An organic model of software of 10 lakh lines
1. Semi detached model, for software project of 2000 lines Effort Estimation E = Ab * (KLOC ) ^ Bb = 3.0 (2) ^ 1.12 = 6.65 Person-month 2. Duration Estimation D= Cb (E) ^ Db = 2.5 (6.65) ^ 0.35 = 4.8 months 3. Persons Estimation P= E/D = 6.65/4.8 = 1.3 persons approximately Thus, 1.3 person can handle this project with approximately 5 months
2. Embedded model of software of 30,000 lines Effort Estimation E = Ab * (KLOC ) ^ Bb = 3.6 (30) ^ 1.2 = 213 Person-month approximately 2. Duration Estimation D= Cb (E) ^ Db = 2.5 (213) ^ 0.32 = 14 months approximately 3. Persons Estimation P= E/D = 213 / 14 = 15 persons approximately Thus, 15 persons can handle this project with approximately 14 months
3. An organic model of software of 1,00,000 lines Effort Estimation E = Ab * (KLOC ) ^ Bb = 2.4 (100) ^ 1.05 = 302 Person-month approximately 2. Duration Estimation D= Cb (E) ^ Db = 2.5 (302) ^ 0.38 = 21 months 3. Persons Estimation P= E/D = 302 / 21 = 14 persons approximately Thus, 14 persons can handle this project with approximately 21 months
4. An organic model of software of 10 lakh lines Effort Estimation E = Ab * (KLOC ) ^ Bb = 2.4 (1000) ^ 1.05 = 3390 Person-month approximately 2. Duration Estimation D= Cb (E) ^ Db = 2.5 (3390) ^ 0.38 = 55 months 3. Persons Estimation P= E/D = 3390 / 55 = 61 persons approximately Thus, 61 person can handle this project with approximately 55 months
