Software Process Control 1 CS 690S Computer Science Seminar Aditya P. Mathur (CS) in collaboration with … João Cangussu (CS) Ray. A. DeCarlo (ECE) Monday November 5, 2001 Newton's Law of Motion in Software Development Processes?
Jan 23, 2016
Software Process Control 1
CS 690S Computer Science Seminar
Aditya P. Mathur (CS)in collaboration with …
João Cangussu (CS)Ray. A. DeCarlo (ECE)
Monday November 5, 2001
Newton's Law of Motion in Software Development Processes?
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Research Question
Can we control the Software Development Process in a manner similar to how physical systems and processes are controlled ?
The central problem in control is to find a technically feasible way to act on a given process so that the process adheres, as closely as possible to some desired behavior. Furthermore, this approximate behavior should be achieved in the face of uncertainty of the process and in the presence of uncontrollable external disturbances acting on the process.
The fundamental control problem (Ref: Control System Design by G. C. Goodwin et al., Prentice Hall, 2001)
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Research Methodology [1]
1. Understand how physical systems are controlled?
2. Understand how software systems relate to physical systems. Are there similarities? Are there differences?
3. Understand the theory and practice of the control of physical systems.
4. Can we borrow from this theory? If “yes,” then proceed further, else drink coffee or tea and think of another research direction.
5. Adapt control theory to the control of SDP and develop models and methods to control the SDP.
6. Study the behavior of the models and methods in real-life settings.
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Research Methodology [2]
7. Improve the model and methods.8. Repeat steps 6 and 7 until you are thoroughly bored or
get rich.
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Feedback Control
Specifications
ProgramEffort +
f(e)Additionaleffort What is f ?
-
RequiredQuality
rQ
ObservedQuality
oQ
oQr
Qe
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Software Development Process: Definitions
A Software Development Process (SDP) is a sequence of well defined activities used in the production of software.
An SDP usually consists of several sub-processes that may or may not operate in a sequence. The Design Process, the Software Test Process, and the Configuration Management Process are examples of sub-processes of the SDP.
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Software Development Process: A Life Cycle
RequirementsElicitation
RequirementsAnalysis
Integrate/Test
Design
Code/Unit test
System test More test DeployNot all feedback loopsare shown.
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Current Focus
Software Test Process (STP): System test phase
Objective:Control the STP so that the quality of the tested software is as desired.
Quantification of quality of software:• Number of remaining errors• Reliability
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Problem Scenario
cp1 cp2 cp3 cp4 cp5 cp6 cp7 cp8 cp9
cpi = check point i
rf
schedule set bythe manager
approximation
r0 observed
deadline
r -
num
ber
ofre
mai
ning
err
ors
t- time
t0
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Our Approach
Actual STP
Controllerrerror(t)
’
w’f
+
+
wf+wf
+
wf+wf
+ STP State Model
robserved(t)
rexpected(t)
sc r0
sc r0
Initial Settings(wf,)
wf
Test Manager
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Physical and Software Systems: An Analogy
Dashpot
Rigid surface
External force
XcurrentXequilibrium
X: Position
Number of remainingerrors
Spring Force
Effective Test Effort
Block
Software
Mass of the blockSoftware
complexity
Quality of thetest process
Viscosity
Spring
To err isHuman.
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Physical Systems: Control
Controllability
Is it possible to control X (r) by adjusting Y (workforce and process quality)?
Observability
Does the system have distinct states that cannot be unambiguously identified by the controller ?
Robustness
Will control be regained satisfactorily after an unexpected disturbance?
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Physical Systems: Laws of Motion [1]
First Law:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
Does not apply to testing because the number of errors does not change when no external effort is applied to the application.
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Physical Systems: Laws of Motion [2]
Newton’s Second Law:
The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.
CDM’s First Law:
The relationship between an complexity Sc of an applications, its rate of reduction in the number of remaining errors, and the applied effort E is E=Sc .
r..
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Physical Systems: Laws of Motion [3]
Third Law:
For every action force, there is an equal and opposite reaction force.
When an effort is applied to test software, it leads to fatigue on the tester.
This is not a scientific relationship.
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Assumption I: CDM’s First Law
The magnitude of the rate of decrease of the remaining errorsis directly proportional to the net applied effort and inverselyproportional to the complexity of the program under test.
cc
srs
r EE
This is derived from Newton’s Second Law of motion.
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Assumption II: CDM’s Second Law
The magnitude of the effective test effort is proportional to theproduct of the applied work force and number of remaining errors.
for an appropriate .
Analogy with the spring:
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Assumption III: CDM’s Third Law
The error reduction resistance is proportional to the error reduction velocity and inversely proportional to the overallquality of the test phase.
rer
1
for an appropriate .
Analogy with the dashpot:
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State Modeletr eeE
r
r
r
r
F
sr
r
ss
wr
rd
ccc
f
10
01
1
010
Fd: Disturbance
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Computing the feedback
teTrtTr max)()(
c
f
c
cc
f
s
w
s
ss
wAI
ˆ
ˆ
ˆ
ˆ1
detdet
2
fwff wwandwhere ˆˆ
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Case Study II: Razorfish Project Description
Project Goal: translate 4 million lines of Cobol code to SAP/R3
A tool has been developed to achievethe goal of this project.
Goal of the test process: (a) Test the generated code, not the tool. (b) Reduce the number of errors by about 85%.
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Validation: Razorfish ProjectTesting Process
Transformer
=
modify
SSAP R/3
run
output 1 output 2
run
SCobol
Select a Test Profile
input
continuetesting yes
no
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Case Study II: Razorfish Project Results
85% reduction achieved.
If the process parameters are not altered then the goal is reached in about 35 weeks.
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Alternatives from Feedback: STP Quality
Desired eigenvalue=-0.152Improving quality alone will not help inachieving the goal.
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Alternatives from Feedback: Workforce
Desired eigenvalue=-0.152 Changing the workforce alone can produce the desired results.
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Alternatives from Feedback: STP quality and workforce
Set of valid choices for changing the quality and the workforce
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Summary
Analogy between physical and software systems presented.
The notion of feedback control of software processes introduced.
One case study described.
Parameter estimation techniques used for model calibration. Made use of system identification techniques.
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Ongoing Research
Expansion of the model to include the entire SDP.
Additional case studies.
Sensitivity analysis:
r is more sensitive to changes in the model parameters during the early stages of the test process than during the later stages.
An improvement in the quality of the STP is more effective than an increase in the workforce.
Brook’s Law was also observed during the analysis.