Software Cost Est & Project Planning Mgt

8/6/2019 Software Cost Est & Project Planning Mgt

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Software Cost & EstimationProject Planning & Control


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To introduce cost and schedule estimation.

To describe several cost estimation

techniques. To describe suggested software estimation

steps

To understand the differences between

software mgt. and other types ofengineering management

Undertstand why project planning isessential in all software projects


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Predicting the resources

required for a softwaredevelopment process


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To establish a budget for a softwareproject.

To provide a means of controlling projectcosts.

To monitor progress against that budget bycomparing planned with estimated costs.

To establish a cost database for futureestimation.

Cost estimation and planning/schedulingare closely related activities.


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Hardware and software costs.

Travel and training costs.

Effort costs (the dominant factor in mostprojects) salaries of engineers involved in the project

costs of building, heating, lighting

costs of networking and communications costs of shared facilities (e.g., library, staff

restaurant)

costs of pensions, health insurance, etc.


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Estimates are made to discover the cost,to the developer, of producing a

software system. There is not a simple relationship

between the development cost and theprice charged to the customer.


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Expert judgment

Estimation by analogy

Parkinsons Law

Pricing to win

Algorithmic cost modelling


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One or more experts in both softwaredevelopment and the application domain usetheir experience to predict software costs.

Process iterates until some consensus isreached.

Advantages: elatively cheap estimationmethod. Can be accurate if experts havedirect

experience of similar systems. Disadvantages: Very inaccurate if there are

noexperts!


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The cost of a project is computed bycomparingthe project to a similar project in the sameapplication domain.

Advantages: Accurate if project dataavailable.

Disadvantages: mpossible if nocomparableproject has been tackled. Needssystematicallymaintained cost database.


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The project costs whatever resources areavailable.

Advantages: No overspending. Disadvantages: System is usually

unfinished.


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The project costs whatever the customerhas to

spend on it. Advantages: ou get the contract.

Disadvantages: The probability that the

customer gets the system he wants issmall.


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Each method has strengths andweaknesses.

Estimation should be based on severalmethods.

If these do not return approximately the

same result, there is insufficientinformation available.

Pricing to win is sometimes the onlyapplicable method.


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Cost is estimated as a mathematicalfunction ofproduct, project and process attributes

whosevalues are estimated by project managers. The function is derived from a study of

historical costing data.

Most commonly used product attribute forcostestimation is LOC (code size).

Most models are basically similar but withdifferent attribute values.


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Developed at TRW, a US defensecontractor.

Based on a cost database of more than 60different projects.

Exists in three stages: Basic - Gives a ball-park estimate based on

productattributes.

Intermediate - modifies basic estimate usingproject andprocess attributes.

Advanced - Estimates project phases and partsseparately.


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Organic mode: Small teams, familiarenvironment, well-understood applications, nodifficult non-functional requirements (EASY).

Semi-detached mode: Project team may

have experience mixture, system may havemore significant non-functional constraints,organization may have less familiarity withapplication (HARDER).

Embedded Hardware/softwaresystems mode:

Tight constraints, unusual for team to havedeep application experience (HARD).


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Organic mode: PM = 2.4 (KDSI) 1.05

Semi-detached mode: PM = 3 (KDSI) 1.12

Embedded mode: PM = 3.6 (KDSI) 1.2

Note: KDSI is the number of thousands of deliveredsource instructions.


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Organic mode project, 32KLOC

PM = 2.4 (32) 1.05 = 91 person months

TDEV = 2.5 (91) 0.38 = 14 months N = 91/15 = 6.5 people

Embedded mode project, 128KLOC

PM = 3.6 (128)1.2

= 1216 person-months TDEV = 2.5 (1216)0.32 = 24 months

N = 1216/24 = 51


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Implicit productivity estimate

Organic mode = 16 LOC/day

Embedded mode = 4 LOC/day

Time required is a function of total effortNOTteam size.

Not clear how to adapt model topersonnelavailability.


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Takes basic COCOMO as starting point.

Identifies personnel, product, computer

andproject attributes which affect cost.

Multiplies basic cost by attribute

multiplierswhich may increase or decrease costs.


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Personnel attributes

Analyst capability

Programmer capability Programming language experience

Application experience

Product attributes Reliability requirement

Database size

Product complexity


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Computer attributes

Execution time constraints

Storage constraints Computer turnaround time

Project attributes

Modern programming practices Software tools

Required development schedule


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These are attributes which were found tobe

significant in one organization with a limitedsize of project history database.

Other attributes may be more significant forother projects.

Each organization must identify its ownattributes and associated multiplier values.


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All numbers in cost model areorganization

specific. The parameters of the modelmust be modified to adapt it to localneeds.

A statistically significant database ofdetailedcost information is necessary.


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Embedded software system onmicrocomputerhardware.

Basic COCOMO predicts a 45 person-montheffort requirement

Attributes = RELY (1.15), STOR (1.21), TIME

(1.10),TOO

L (1.10) Intermediate COCOMO predicts 45*1.15*1.21.1.10*1.10 = 76 person-months.

Total cost = 76*$7000 = $532,000


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Step 1:Gather and AnalyzeSoftware Functional &

ProgrammaticRequirements


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Step 2:Define the Work

Elements and Procurements


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Step 3:Estimate Software

Size Step 4:Estimate Software

Effort


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Step 5:Schedule the effort

Step 6:Calculate the Cost

Step 7:Determine the

Impact of Risks


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Step 8:Validate and Reconcile theEstimate Via Models and Analogy

Step 9:Reconcile Estimates, Budget, andSchedule

Step 10: Review and Approve the

Estimates


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Step 11: Track, Report, andMaintain the Estimates


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The product is intangible

There are no standard softwareprocesses

Large software projects areoften one-off projects


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Reportwritingandpresentation

Personnelselectionandevaluation

Project monitoring & reviews

Product costing

Projectplanningandscheduling

Proposalwriting


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Quality lan

Validationlan

ConfigurationManagement

lan

Maintenancelan

Staff

developmentlan


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Introduction

ProjectOrganisation

Risk Analysis

Hardware & Softwareresource requirements

Work Breakdown

Project Schedule

Monitoring & Reporting

Mechanism


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Milestone is an end point of asoftware process activity

Milestone is an end point of asoftware process activity

Deliverable is a project result that isdelivered to the customer , usuallydelivered at the end of a projectphase such as specifications and

design

Deliverable is a project result that isdelivered to the customer , usuallydelivered at the end of a projectphase such as specifications and

design

Deliverables are usually milestonesbut milestones need not be

deliverables

Deliverables are usually milestonesbut milestones need not be

deliverables


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Estimate the project cost to the supplierthen decide on the price to the

customer. Prepare cost estimates using different

techniques. Estimates should becomparable.

The time required to complete a projectis not simply proportional to the numberof people working on the project.


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Algorithmic cost estimation is difficultbecause of the need to estimateattributes of the finished product.

Algorithmic cost models are a useful aidto project managers as a means ofcomparing different development

options. The time required to complete a project

is not simply proportional to the numberof people working on the project.


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Software Cost Est & Project Planning Mgt

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