Big
The use of Comparator tools in Estimation
Andy Nolan BSc Hons, CEng, FBCS, CITP
Chief of Software improvement – The Software Centre of Excellence
Satpaul Sall BSc Hons
Software Technologist
– The Software Centre of Excellence
©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

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3 A Brief History of Engine Controls
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The Control Systems department is responsible for the Engine
Electronic Controllers (EECs) for a range of small and large gas turbine engines for the aerospace industry.
The software is developed to DO-
178B Level-A standards
The company has been developing high integrity software for over 20 years and has extensive data on its processes and productivity.
We have the largest order book in history, new engine development places greater demand on the software team (shorter time scales and lower costs)
Rolls-Royce data

Benchmarking the business
CO-Bus-MO
Enterprise business performance
Estimation & eliciting key assumptions & negotiation
Software
Supplier
COCOMO
Challenging our supplier costs.
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CO-RISK-MO
Risk
Management
COCOMO
A unifying language
Hardware
COCOMO
Using the model to identify and quantify risk
CO-Imp-MO
Improvement
COCOMO
Using COCOMO to identify & validate improvements
Hardware
Supplier
COCOMO
Using many SW factors to estimate hardware engineering
Rolls-Royce data

©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

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Lower
Cost
Size
Higher
Cost
Size (the product): The magnitude (or quantity) of a task.
• Size
•
•
•
Complexity
Reuse
Risk/Uncertainty
Environment: The environment in which you build the product
•
•
•
•
•
Processes & tools
People
Management
Organisation
Etc
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Historic Baseline
Historic Size
Historic
Environment
(a definition of the project environment)
Delta
Create a scaling Factor that represents the differences between the two projects in both size and environment
Actual historic cost
New Project
New Size
New
Environment
(a definition of the project environment)
New cost = Historic cost * Delta
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An “Absolute” estimation tool was developed for
Hardware by relating hardware complexity to software lines of code.
This relationship is hidden from the estimator who only has to select hardware units they are working on
New Project
Standard job hours
Size
(task and unit)
Environment
(a definition of the project environment) cost = Standard Job
* Size *
Environment
Rolls-Royce data
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©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

 Business Challenge
 Can we use COCOMO to estimate the cost of a whole engine?
 Effort
 We have 8 hours to demonstrate this capability!
 Approach
 Use Comparator method based on COCOMO II

Relate all aspects to a nominal “Baseline” project
 COCOMO II factors to be completed by Chief Design Engineer
 No underlying factors to be altered
– only the constant “C”
 Leave 1 project aside as a test of calibration (project 6)
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Environment: Relative (COCOMO II factors)
Engine 1 Engine 2 Engine 3 Engine 4 Engine 5 Engine 6
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The only show in town – high priority. Single site project, stable team
Stable requirements, higher precedence, team more experienced, single site team, improved process maturity., high levels of reuse
Stable requirements, higher precedence, single site team, improved process maturity. Improved management
High requirements volatility, low
TRL, low process maturity, low team experience, low management experience and high schedule pressure
High Schedule pressure
Lower requirements change, team cohesion, process maturity, experienced team
Low requirements volatility, high team cohesion, high precedence, mature processes, experienced team, low schedule pressure, experienced management team
High process maturity,
Some architectural issues. Drop in team experience, high turnover of staff, multi site working
Requirements change, loss of precedence, inexperienced team, architectural issues, loss of team cohesion, schedule pressure, new management team, multi site project, staff turnover
Loss of precedence, some architectural issues, schedule pressure, multi site project, high staff turnover
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 Size
 REVL
 PREC
 FLEX
 RESL
 TEAM
 PMAT
 SCED
 Management
Expereince
 Based on the survey, these factors correlated well with cost.
This does not mean the other factors do not – rather it means that these were the factors the interviewee understood well.
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Predicted & Actual costs – A close correlation
Calibrate to these projects
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Baseline
Estimate this project
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1
4
2
B
5
3
6
Size (AMF) – not to scale
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 Size is not the only determining factor for cost – the environment is also proving critical for project success.
 From a simple analysis, it would seem that COCOMO II can be used to “model” the development environment
 The Rolls-Royce Environment is changing and COCOMO II predicts that this is creating a headwind
 The exercise has the side effect of training the business leaders in the factors that affect cost
Rolls-Royce data

©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

 COCOMO II is a language that bridges between engineering and the business
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 It is also the bridge between different areas of the business
 It has been used to help benchmark the business
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 You can interpolate and extrapolate within a domain but not across domains
(unless you have a domain bridge function)
 COCOMO II appears to work on engineering practices where requirements are translated into implementation through an engineering process
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