SSVV 01a Intro

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OutlineFamous Software bugs

What is a bug?Software quality assessment

Questions

Software Systems Verication and ValidationLecture 01a - Introduction

Lect. dr. Andreea Vescan

Babeş-Bolyai UniversityCluj-Napoca

2014-2015

Lect. dr. Andreea Vescan Software Systems Verication and Validation

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1 Famous Software bugsFirst bugFamous Software bugs

2 What is a bug?

Terms for software failuresWhen?Why?Cost?Quality assessment

3 Software quality assessment

Verication and Validation

4 QuestionsQuestions


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First bugFamous Software bugs

First bug

Grace Hopper - About rst software bug:https://www.youtube.com/watch?v=lQS0hDqpVLE1947 - Harvard University - Mark II


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First bug


The rst computer bug was born!




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First bug


The rst computer bug was born!

Well, okay, it died!Lect. dr. Andreea Vescan Software Systems Verication and Validation

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Mariner

1962


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Mariner

1962


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Mariner

1962

Disaster: The Mariner 1 rocket diverted from its intendedight path shortly after launch.


Outline

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Mariner

1962


Cause: A programmer incorrectly transcribed a handwrittenformula into computer code.


Outline

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Mariner

1962


Cause: A programmer incorrectly transcribed a handwrittenformula into computer code.Cost: $ 18.5 million


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World War III - almost

1983


Outline

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Famous Software bugsWhat is a bug?

Software quality assessmentQuestions



1983


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1983

Disaster: The Soviet early warning system falsely indicatedthe United States had launched ve ballistic missiles.


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1983

Disaster: The Soviet early warning system falsely indicatedthe United States had launched ve ballistic missiles.Cause: A bug in the Soviet software failed to lter out falsemissile detections caused by sunlight reecting off cloud-tops.


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1983

Disaster: The Soviet early warning system falsely indicatedthe United States had launched ve ballistic missiles.Cause: A bug in the Soviet software failed to lter out falsemissile detections caused by sunlight reecting off cloud-tops.Cost: Nearly all of humanity


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Therac-25 radiation therapy machine

1985


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1985



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1985

Disaster: Canadas Therac-25 radiation therapy machinemalfunctioned and delivered lethal radiation doses to patients.



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1985

Disaster: Canadas Therac-25 radiation therapy machinemalfunctioned and delivered lethal radiation doses to patients.Cause: Because of a subtle bug called a race condition, atechnician could accidentally congure Therac-25 so theelectron beam would re in high-power mode without theproper patient shielding.


OutlineFamous Software bugs b

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1985

Disaster: Canadas Therac-25 radiation therapy machinemalfunctioned and delivered lethal radiation doses to patients.Cause: Because of a subtle bug called a race condition, atechnician could accidentally congure Therac-25 so theelectron beam would re in high-power mode without theproper patient shielding.Cost: Three people dead, three people critically injured


OutlineFamous Software bugs Fi b

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gWhat is a bug?



Pentium Fails Long Division

1993


OutlineFamous Software bugs First bug

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gWhat is a bug?




1993



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1993

Disaster: Intels highly-promoted Pentium chip occasionallymade mistakes when dividing oating-point numbers within aspecic range.



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1993

Disaster: Intels highly-promoted Pentium chip occasionallymade mistakes when dividing oating-point numbers within aspecic range.Cause: The divider in the Pentium oating point unit had a

awed division table, missing about ve of a thousand entriesand resulting in these rounding errors.



h i b ? First bug

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1993

Disaster: Intels highly-promoted Pentium chip occasionallymade mistakes when dividing oating-point numbers within aspecic range.Cause: The divider in the Pentium oating point unit had a

awed division table, missing about ve of a thousand entriesand resulting in these rounding errors.Cost: $475 million, corporate credibility.



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gFamous Software bugs

Disney’s Lion King

1995



What is a bug? First bug

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gFamous Software bugs


1995




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Famous Software bugs


1995

Disaster: The Disney company released its rst multimediacd-rom game for children, The Lion King Animated Storybook . Several parents couldn’t get the software to work.




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1995


Cause: Disney failed to test the software on a broadrepresentation of the many different PC models available onthe market.



What is a bug? First bugF S f b

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1995


Cause: Disney failed to test the software on a broadrepresentation of the many different PC models available onthe market.Cost: cd-rom replacements, corporate credibility.



What is a bug? First bugF S ft b g

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gSoftware quality assessment

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Ariane Rocket

1996



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gSoftware quality assessment

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Ariane Rocket

1996




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Ariane Rocket

1996

Disaster: Ariane 5, Europes newest unmanned rocket, wasintentionally destroyed seconds after launch on its maidenight.




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Ariane Rocket

1996


Cause: Shutdown occurred when the guidance computer triedto convert the sideways rocket velocity from 64-bits to a16-bit format.



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Ariane Rocket

1996


Cause: Shutdown occurred when the guidance computer triedto convert the sideways rocket velocity from 64-bits to a16-bit format.Cost: $500 million.


OutlineFamous Software bugsWhat is a bug?

Software quality assessment


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Mars Climate Crasher

1998





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1998





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1998

Disaster: After a 286-day journey from Earth, the MarsClimate Orbiter red its engines to push into orbit aroundMars. The engines red, but the spacecraft fell too far intothe planets atmosphere, likely causing it to crash on Mars.





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1998


Cause: The software that controlled the Orbiter thrustersused imperial units (pounds of force), rather than metric units(Newtons) as specied by NASA.





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1998


Cause: The software that controlled the Orbiter thrustersused imperial units (pounds of force), rather than metric units(Newtons) as specied by NASA.Cost: $125 million.





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Cancer Treatment

2000





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Cancer Treatment

2000





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Cancer Treatment

2000

Disaster: Radiation therapy software by Multidata SystemsInternational miscalculated the proper dosage, exposingpatients to harmful and in some cases fatal levels of radiation.



Software quality assessmentQ i


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Cancer Treatment

2000

Disaster: Radiation therapy software by Multidata SystemsInternational miscalculated the proper dosage, exposingpatients to harmful and in some cases fatal levels of radiation.Cause: The software calculated radiation dosage based on theorder in which data was entered, sometimes delivering adouble dose of radiation.



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Cancer Treatment

2000

Disaster: Radiation therapy software by Multidata SystemsInternational miscalculated the proper dosage, exposingpatients to harmful and in some cases fatal levels of radiation.Cause: The software calculated radiation dosage based on theorder in which data was entered, sometimes delivering adouble dose of radiation.Cost: Eight people dead, 20 critically injured.




Terms for software failuresWhen?Why?Cost?



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Terms for software failures





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Failure : A failure is said to occur whenever the externalbehavior of a system does not conform to that prescribed inthe system specication.





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Failure : A failure is said to occur whenever the externalbehavior of a system does not conform to that prescribed inthe system specication.Error : An error is a state of the system. In the absence of anycorrective action by the system, an error state could lead to afailure which would not be attributed to any event subsequentto the error.





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Failure : A failure is said to occur whenever the externalbehavior of a system does not conform to that prescribed inthe system specication.Error : An error is a state of the system. In the absence of anycorrective action by the system, an error state could lead to afailure which would not be attributed to any event subsequentto the error.Fault : A fault is the adjudged cause of an error.







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Process of failure manifestation - represented as a behaviorchain:







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Process of failure manifestation - represented as a behaviorchain:fault → error → failure.




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Process of failure manifestation - represented as a behaviorchain:fault → error → failure.

In this course, all software problems will be called bugs.




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When a software bug occurs?

A software bug occurs when one or more of the following rules istrue [Patton]:




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The software doesn’t do something that the productspecication says it should do.




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The software does something that the product specicationsays it shouldn’t do.




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The software does something that the product specicationsays it shouldn’t do.The software does something that the product specicationdoesn’t mention.




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The software does something that the product specicationsays it shouldn’t do.The software does something that the product specicationdoesn’t mention.The software doesn’t do something that the productspecication doesn’t mention but should.




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The software does something that the product specicationsays it shouldn’t do.The software does something that the product specicationdoesn’t mention.The software doesn’t do something that the productspecication doesn’t mention but should.The software is difficult to understand, hard to use, slow, orinthe software tester’s eyeswill be viewed by the end user as justplain not right.




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Why do bugs occur?




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The cost of bugs




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The cost of bugs




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Software quality

Software quality: Conformance to explicitly stated functionaland performance requirements, explicitly documenteddevelopment standards, and implicit characteristics that areexpected of all professionally developed software. [Pressman]




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Software quality


Activities for software quality assessment




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Software quality


Activities for software quality assessmentStatic analysis




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Software quality



Dynamic analysis.




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Software quality



Based on the examination of a number of documents. It doesnot involved actual execution of the code under development.

Dynamic analysis.




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S ft lit

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Software quality



Based on the examination of a number of documents. It doesnot involved actual execution of the code under development.Includes: code review, inspection, algorithm analysis, proof of

correctness.Dynamic analysis.




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Software quality




correctness.Dynamic analysis.Involved actual program execution in order to expose possibleprogram failures.




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Soft are q alit

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Software quality




correctness.Dynamic analysis.Involved actual program execution in order to expose possibleprogram failures.Includes: testing.




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Verication and Validation (SEI and NASA)

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Software Engineering InstituteNASA - Software Assurance Guidebookand Standard




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Software Engineering InstituteVerication

Validation

NASA - Software Assurance Guidebookand Standard




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Software Engineering InstituteVericationassures the product isdeveloped according torequiremets, specications

and standards.

Validation

assures that the product willbe usable on the market.



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and standards.building the product correctly.

Validation

assures that the product willbe usable on the market.building the correct product.



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and standards.building the product correctly.Are we building the productright?

Validation

assures that the product willbe usable on the market.building the correct product.Are we building the rightproduct?



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Validation





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Famous Software bugsWhat is a bug?Software quality assessment

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Validation




the process that assures that thesoftware product:


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Validation




the process that assures that thesoftware product:will satisfy the requirement(functional and others) =validation.


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Validation




the process that assures that thesoftware product:will satisfy the requirement(functional and others) =validation.every step in the product

development is resulting in acorrect(sub)product=verication.


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Verication and Validation - comparison

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Vericationevaluates if the product of agiven development phase

satises the requirements of that phase;

Validationhelps us at conrming that a productmeets its intended use.


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Vericationevaluates if the product of agiven development phasesatises the requirements of that phase;reviews products to ensure theirquality (consistency,completness, correctness);

Validationhelps us at conrming that a productmeets its intended use.is performed toward the end of thesystem development to determine if the entire system meets thecustomers’s needs and expectations;

Lect. dr. Andreea Vescan Software Systems Verication and Validation Outline


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Vericationevaluates if the product of agiven development phasesatises the requirements of that phase;reviews products to ensure theirquality (consistency,completness, correctness);

static and dynamic analysistechiques.

Validationhelps us at conrming that a productmeets its intended use.is performed toward the end of thesystem development to determine if the entire system meets thecustomers’s needs and expectations;is performed on the entire system by

actually running the system in its reaenvironment and using a variety of tests.



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Thank You For Your Attention!



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Thank You For Your Attention!

Lect dr Andreea Vescan Software Systems Verication and Validation

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