The Missing Links in Software Estimation: Work, Team Loading and Team Power

Luigi Buglione

Engineering.IT (Italy)

luigi.buglione@eng.it

Çiğdem Gencel

Free University of Bozen-Bolzano (Italy)

cigdem.gencel@unibz.it

IWSM - MENSURA , 5-7 October 2016, Berlin

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Software Estimation

Problem

Fundamental Concepts: • Energy & Work • Team Loading • Team Power

Implications to Understanding

and Theory Development

Empirical Investigations

Conclusions

Software Effort Estimation – State of the Art 3

Effort Estimation Methods

Parametric

Empirically based

Statistical Analysis

Theory based

Non-parametric

Expert based

Informal Analogy

Structured Analogy

Learning based

Case Based

Reasoning Neural

Networks Fuzzy Logic

Composite

Concepts Revisited: Energy & Work

•  In physics, potential energy is defined as ‘the capacity of something to do work’

•  In SE, it can be defined as the team’s cumulative intellectual work capacity within a development environment for developing a piece of software during a period of time.

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Transformation of Energy 5

•  The law of the conservation of energy says: •  Energy can be transformed from one form to another

Transformation of Energy in Software Development 6

Team Time Scope Quality

Work Input Work Output

Wastes

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•  Wintput is the ‘work capacity of a software team’ that is input in a project

•  WOutput corresponds to ‘valuable work’ that produces a piece of software with some characteristics:

•  Productivity of software development is denoted as:

!!"#$"# = !(!"#$%&'#()&%*,!"#$%&'()*,!"#$%&')

!"#$%&'()('* (!) =!!"#$"#!!"#$%

Concepts Revisited: Efficiency (Productivity)

•  Any waste in development would decrease productivity.

•  Many studies investigated the factors affecting Woutput and hence Productivity:

•  Team factors, •  Process factors •  Project related factors •  …

•  This presentation instead focuses on clarification of concepts and laying the foundations

•  In particular we investigated TeamPower and Team Loading concepts

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Concepts Revisited: Efficiency (Productivity)

In physics, Power (P) is defined as “the rate of doing work (or similarly, rate which energy is transferred)”.

The term “horsepower” was introduced by James Watt; famous for his work on improving the performance of steam engines

Concepts Revisited: Power

•  The power of a system may stay constant or change over time.

•  Therefore, power is usually expressed in three ways: •  Instantaneous Power, which is the power measured at a given

instant in time;

•  Peak Power, which corresponds to is the maximum value the instantaneous power can have over a period of time;

•  Average Power, which is the amount of work done divided by the time interval that it took to do the work.

•  One way to calculate this is to find the area under the power versus time curve (which gives the total work done) and divide by the total time.

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Concepts Revisited: Power

•  In software engineering, we can define ‘TeamPower’ for expressing the rate of doing work (or rate of transferring their intellectual energy to produce a piece of software).

•  This measure is commonly referred to as Speed or Speed of Delivery in software engineering!

!"#$%&# !"#$ !"#$% =!!"#!"#!"#$

Concepts Revisited: Team Power

Concepts Revisited: Team Loading

• On the other hand, WInput is dynamic and changes during the life cycle depending on: •  the project requirements and constraints, •  how management schedules software engineering tasks and

allocates people to these tasks.

• Hence, there is another important concept:

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!"#$%&# !"#$ !"#$%&' =!!"!"#!"#$

Transformation of Energy in Software Development 13

WInput / Time

Wastes

WOutput / Time

Team Loading Team Power

Concepts Revisited: Terms & Units Inconsistencies

•  In SE, even though a similar term ‘manpower’ has been used, the inconsistent and sometimes fallacious use of the term resulted in consequent misconceptions.

•  Norden referred to Team Loading as ‘Manpower loading (man-months/year)’.

•  Putnam refers to the term several times but with inconsistent use of the term as well as the units of measure (e.g. Manpower (people/year), Manpower (man-months) and Cumulative effort (total people))

•  The ISBSG introduced another measure called ‘Manpower delivery rate (size/time x max team size)’ which is claimed to provide a measure of Speed but also including the Team size.

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Team Loading during Development

•  Brooks stated that estimating techniques fallaciously confuse work effort with progress by hiding the assumption that men and months are interchangeable.

•  He then explained that this is only possible when a task

can be partitioned among many workers with no communication among them.

•  His hypotheses were brilliant, and therefore have gained considerable attention by the community.

Core concepts revisited Some Important Misconceptions Fred Brooks: Adding manpower to a late software project makes it later

Fred Brooks: Adding manpower to a late software project makes it later

Team Loading was expressed in a unit of number of people, referring to the number of people working in the team.

19 Steven Kareem Jim

A Thought Experiment

The Relationship between Team Loading, TeamPower and Productivity

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Productivity (Woutput/Winput)

α α

•  How is it possible to increase the rate of

work: Avg. Team Power?

We investigated the nature of the relationship between Avg Team Loading and Avg. Team Size using the ISBSG dataset

•  We prepared the data for analysis as follows: ü  Data Quality Rating (DQR): A or B Rating ü  Business Applications ü  New Development ü  Recording method: Person-hrs ü  Resource Level: 1 ü  Ratio of Project Work Effort to Non-Project Activity: projects that have

90-100% ü  Normalized Work Effort (person-hrs) used ü  The project duration is calculated by subtracting project inactive time

from the total duration (1 month = 120 hrs).

Empirical Investigations – ISBSG dataset

22 Empirical Investigation - COSMIC

•  Project sizes: 11-966 CFP (most below 300 CFP) •  Avg. Team Loading for some projects are much

higher than Avg. Team Size

•  Avg. Team Loading in some cases below 1 person!

23 Empirical Investigation - IFPUG

•  Project sizes: 34-4887 IFPUG FP (most below 2000 FP) •  Avg. Team Loading for some projects are much lower than

Avg. Team Size

•  Avg. Team Loading in some cases below 1 person

•  Consistent use of concepts and terms are very important in knowledge and theory development in SE

•  Benchmark datasets should include both Productivity and Avg Team Power figures in addition to Avg. Team Size for better understanding and fair comparisons

•  The empirical investigations of this study indicate: •  Some theoretical reasons of high variations in productivity

figures •  Reveal poor planning practices •  Research need for best ways to increase Team Loading (e.g.

overtime/time-shifts by distributing work globally etc. )

Conclusions