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COCOMO Model

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Software EngineeringAssignment Submitted by:Amrith Krishna, Roll No: 5, S5 CSE ACOCOMO model was developed by Boehm. Its a top-down multi-variable model. The model calculates the effort in terms of person-months. The steps: 1. Obtain an initial estimate of the development effort from the estimate of thousands of delivered lines of source code (KDLOC). 2. Determine a set of 15 multiplying factors from different attributes of the project. 3. Adjust the effort estimate by multiplying the initial estimate with all the multiplying factors.1. Initial EstimateWe estimate the initial effort, Ei with a single static variable i.e. KDLOC and 2 constants a Multiplicative factor b- exponential factor Ei = a x KDLOCb. Projects can be classified as 3 in COCOMO model, and their corresponding global values for a and b are;2. Determining Cost driver attributesThere are 15 different attributes, called cost driver attributes that determine the multiplying factors. These factors depend on product, computer, personnel, and technology attributes called project attributes.Ratings Cost Drivers Product attributes Required software reliability Size of application database Complexity of the product Hardware attributes Run-time performance constraints Memory constraints Volatility of the virtual machine environment Required turnabout time Personnel attributes Analyst capability Applications experience Software engineer capability Virtual machine experience 1.46 1.29 1.42 1.21 1.19 1.13 1.17 1.10 1.00 1.00 1.00 1.00 0.86 0.91 0.86 0.90 0.71 0.82 0.70 0.87 0.87 1.00 1.00 1.00 1.00 1.11 1.06 1.15 1.07 1.30 1.21 1.30 1.15 1.66 1.56 0.70 0.75 0.88 0.94 0.85 1.00 1.00 1.00 1.15 1.08 1.15 1.40 1.16 1.30 1.65 Very Low Low Nominal High Very High Extra HighProgramming language experience Project attributes Application of software engineering methods Use of software tools Required development schedule1.141.071.000.951.24 1.24 1.231.10 1.10 1.081.00 1.00 1.000.91 0.91 1.040.82 0.83 1.10The multiplying factors for ah 15 cost drivers are multiplied to get the effort adjustment factor (EAF). EAF = product of all multiplication factors.3. Final EffortThe final effort estimate, E, is obtained by multiplying the initial estimate by the EAFE = EAF x Ei By this method, the overall cost of the project can be estimated. For planning and monitoring purposes, estimates of the effort required for the different phases is also desirable. In COCOMO, effort for a phase is a defined percentage of the overall effort. The percentage of total effort spent in a phase varies with the type and size of the project .Example The sizes for the different modules and the overall system are:Ei = 3.2 x 3^1.05 = 10.14 PM EAF = 1.15 x 1.06 x 1.13 x 1.17 =1.61 E = 10.14 x 1.61 =16.3 PMReferences:1. An integrated approach to Software Engineering - Pankaj Jalote, Narosa Publication 2. Software Engineering - Roger S. Pressman, Tata McGraw Hill