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SQA UNIT I FUNDAMENTALS OF SOFTWARE QUALITY ENGINEERING

Concepts of Quality-Hierarchical Modeling-

Quality Models- Quality Criteria And its Interrelation –

Fundamentals of Software Quality Improvement-

Concepts of Process Maturity- Improving Process Maturity

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LEARNING ABOUT EACH OTHER

Who am I? This talk is based on Workshops and

sessions in STTPs, college,

Publication in conferences and journals

discussions with academicians

some experimentation.

Who are You? Background Qualification Experience Pre requisite

Mapping expectations

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SYLLABUS

Term work Two tests, One Presentation/Case Study Six assignments based on the recommended

syllabus: Unit I: 1 Unit II: 1 Unit III: 2 Unit IV: 1 Unit V: 1

Submission: Every next week after unit is complete

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BEFORE WE BEGIN……..

Agenda Concepts of Quality Hierarchical Modeling- Quality Models Quality Criteria And its

Interrelation Fundamentals of

Software Quality Improvement-

Concepts of Process Maturity- Improving Process Maturity

You can at any time in the session: Interrupt Comment Share experience

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DID YOU KNOW?

..\BVIT\Did You Know 3.0 (Officially updated for 2012) HD.mp4

SOME FAMOUS SOFTWARE ERRORS

Patriot Missile System

NASA's Mars Polar Lander

ESA's Ariane 5 Launch System

PATRIOT MISSILE SYSTEM

On February 25, 1991, the Patriot missile battery at Dharan, Saudi Arabia had been in operation for 100 hours, by which time the system's internal clock had drifted by one third of a second. For a target moving as fast as an inbound TBM, this was equivalent to a position error of 600 meters.

The radar system had successfully detected the Scud and predicted where to look for it next, but because of the time error, looked in the wrong part of the sky and found no missile. With no missile, the initial detection was assumed to be a spurious track and the missile was removed from the system. No interception was attempted, and the missile impacted on a barracks killing 28 soldiers.

MARS POLAR LANDER The last telemetry from Mars Polar Lander was sent just prior

to atmospheric entry on December 3, 1999. No further signals have been received from the lander. The cause of this loss of communication is unknown.

According to the investigation that followed, the most likely cause of the failure of the mission was a software error that mistakenly identified the vibration caused by the deployment of the lander's legs as being caused by the vehicle touching down on the Martian surface, resulting in the vehicle's descent engines being cut off whilst it was still 40 meters above the surface, rather than on touchdown as planned.

Another possible reason for failure was inadequate preheating of catalysis beds for the pulsing rocket thrusters

ARIANE 5 ROCKET June 4, 1996 was the first test flight of the Ariane 5 launch system. The

rocket tore itself apart 37 seconds after launch, making the fault one of the most expensive computer bugs in history.

The Ariane 5 software reused the specifications from the Ariane 4, but the Ariane 5's flight path was considerably different and beyond the range for which the reused code had been designed. Specifically, the Ariane 5's greater acceleration caused the back-up and primary inertial guidance computers to crash, after which the launcher's nozzles were directed by spurious data. Pre-flight tests had never been performed on the re-alignment code under simulated Ariane 5 flight conditions, so the error was not discovered before launch.

Because of the different flight path, a data conversion from a 64-bit floating point to 16-bit signed integer caused a hardware exception (more specifically, an arithmetic overflow, as the floating point number had a value too large to be represented by a 16-bit signed integer). Efficiency considerations had led to the disabling of the exception handler for this error. This led to a cascade of problems, culminating in destruction of the entire flight.

2003 NORTH AMERICA BLACKOUT August 14, 2003

12:15 p.m. Inaccurate data input renders a system monitoring tool in Ohio ineffective. 1:31 p.m. The Eastlake, Ohio, generating plant shuts down. 2:02 p.m. First 345-kV line in Ohio fails due to contact with a tree in Walton Hills, Ohio. 2:14 p.m. An alarm system fails at FirstEnergy's control room and is not repaired. 2:27 p.m. Second 345-kV line fails due to tree. 3:05 p.m. A 345-kV transmission line fails in Parma, south of Cleveland due to a tree. 3:17 p.m. Voltage dips temporarily on the Ohio portion of the grid. Controllers take no action, but power shifted by

the first failure onto another 345-kV power line causes it to sag into a tree. While Mid West ISO and FirstEnergy controllers try to understand the failures, they fail to inform system controllers in nearby states.

3:39 p.m. A First Energy 138-kV line fails. 3:41 and 3:46 p.m. Two breakers connecting FirstEnergy’s grid with American Electric Power are tripped as a 345-

kV power line and 15 138-kV lines fail in northern Ohio. Later analysis suggests that this could have been the last possible chance to save the grid if controllers had cut off power to Cleveland at this time.

4:06 p.m. A sustained power surge on some Ohio lines begins uncontrollable cascade after another 345-kV line fails.

4:09:02 p.m. Voltage sags deeply as Ohio draws 2 GW of power from Michigan. 4:10:34 p.m. Many transmission lines trip out, first in Michigan and then in Ohio, blocking the eastward flow of

power. Generators go down, creating a huge power deficit. In seconds, power surges out of the East, tripping East coast generators to protect them, and the blackout is on.

4:10:37 p.m. Eastern Michigan grid disconnects from western part of state. 4:10:38 p.m. Cleveland separates from Pennsylvania grid. 4:10:39 p.m. 3.7 GW power flow from East through Ontario to southern Michigan and northern Ohio, more than ten

times larger than the condition 30 seconds earlier, causing voltage drop across system. 4:10:40 p.m. Flow flips to 2 GW eastward from Michigan through Ontario, then flip westward again in a half second. 4:10:43 p.m. International connections begin failing. 4:10:45 p.m. Western Ontario separates from east when power line north of Lake Superior disconnects. First

Ontario plants go offline in response to unstable system. Quebec is protected because its lines are DC, not AC. 4:10:46 p.m. New York separates from New England grid. 4:10:50 p.m. Ontario separates from Western New York

grid. 4:11:57 p.m. Last lines between Michigan and Ontario fail. 4:13 p.m. End of cascade. 256 power plants are off-line. 85% went offline after the grid

separations occurred, most of them on automatic controls. 50 million people without power.

CAUSES OF SOFTWARE ERRORS

1. faulty requirements definition

2. client-developer communication failures

3. deliberate deviations from software requirements

4. logical design errors

5. coding errors

6. non-compliance with documentation and coding instructions

7. shortcomings of the testing process

8. procedure errors

9. documentation errorstext section 2.3

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CONCEPTS OF QUALITY

WHAT IS QUALITY? Quality is conformance to specifications (British Defense Industries

Quality Assurance Panel) Quality is conformance to requirements: Phil Crosby Quality is fitness for purpose or use: Juran Quality is a predictable degree of uniformity and dependability, at

low cost and suited to the market: Edward Deming Quality is synonymous with customer needs and expectations: R J

Mortimoys Quality is meeting the (stated) requirements of the customer- now

and in the future: Mike Robinson Quality is the total composite product and service characteristics

of marketing, engineering, manufacturing and maintenance through which the product and service in use will meet the expectations by the customer: Arman Feiganbaum

Totality of characteristics of an entity that bear on its ability to satisfy stated and implied needs: ISO 8402: 1994

DEFINITION OF"SOFTWARE QUALITY"Pressman's Conformance to explicitly stated functional and performance requirements, explicitly documented development standards, and implicit characteristics that are expected of all professionally developed software.

1. IEEE’s2. The degree to which a

system, component, or process meets specified requirements.

3. The degree to which a system, component, or process meets customer or user needs or expectations.

IEEE DEFINITION OF"SOFTWARE QUALITY ASSURANCE"

1. A planned and systematic pattern of all actions necessary to provide adequate confidence that an item or product conforms to established technical requirements.

2. A set of activities designed to evaluate the process by which the products are developed or manufactured. Contrast with quality control.

CMM"The Capability Maturity Model for Software developed by the SEI is a framework that describes the key elements of an effective software process. The CMM describes an evolutionary improvement path for software organizations from an ad hoc, immature process to a mature, disciplined one.“

"The CMM covers practices for planning, engineering, and managing software development and maintenance. When followed, these practices improve the ability of organizations to meet goals for cost, schedule, functionality, and product quality."

WHAT IS A PRODUCT?

A generic term that refers to Goods Services

Failure to meet quality requirements in either dimension can have serious negative consequences

Product characteristics: Functionality Reliability Usability Efficiency Maintainability Portability

DIFFERENCE BETWEENQUALITY AND GRADE Software Scenario 1

High quality (no bugs, readable manual) Low grade (limited number of features)

Software Scenario 2 Low quality (many bugs, poorly organized user

documentation) High grade (numerous features)

Quality Management Issues Customer satisfaction

Conformance to requirements Fitness for use

Prevention over inspection Management responsibility

QUALITY MANAGEMENT PROCESSES

Quality Planning involves identifying which quality standards are relevant to the project and determining how to satisfy them

Quality Assurance is all the planned and systematic activities implemented within the quality system to provide confidence that the project will satisfy the relevant quality standards.

Quality Control involves monitoring specific project results to determine if they comply with relevant quality standards, and identifying ways to eliminate causes of unsatisfactory results

PREVENTION AND INSPECTION

Prevention Keeping errors out of the process

Inspection Keeping errors put of the hands of the customer.

SOFTWARE QUALITY – GATES & GM

At a COMDEX exposition, Bill Gates stated, “If General Motors had kept up with technology like the computer industry has, we would all be driving twenty-five dollar cars that got 1000 miles to the gallon.”

In response to Gates’ comments, General Motors issued a press release stating, “If GM had developed technology like Microsoft, we would all be driving cars with the following characteristics:

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SOFTWARE QUALITY – GATES & GM

For no reason whatsoever your car would crash twice a day.

Every time they repainted the lines on the road you would have to buy a new car.

Occasionally your car would die on the freeway for no reason, and you would just accept this, restart, and drive on.

Occasionally, executing a maneuver such as a left turn, would cause your car to shut down and refuse to restart, in which case you would have to reinstall the engine.

The airbag system would say ‘Are you sure?’ before going off. 23

SOFTWARE QUALITY – GATES & GM

Occasionally, for no reason whatsoever, your car would lock you out and refuse to let you in until you simultaneously lifted the door handle, turned the key, and grabbed hold of the radio antenna.

Every time GM introduced a new model car, buyers would have to learn how to drive all over again because none of the controls would operate in the same manner as the old car.

You would press the Start button to shut off the engine.

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QUALITY MATTERS

Software quality is a critical success factor. Software quality must:

Have the support of the management Be planned early in the design phase Be understood and followed by everyone on

the team Be monitored continuously Be documented for accountability and

reference

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QUALITY MATTERS

Several factors influenced system developers to consider system quality: End user computing environment User friendly tools User satisfaction as surrogate for system

success Fourth generation languages/products

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QUALITY ADVANTAGE

Emphasis on quality has several advantages: Financial – maintenance, time Operational – rework, bugs Legal – privacy, security Contractual – compliance Customer relation – CRM Reputation – image Moral – being part of a winning team Appraisal – performance evaluation

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HIERARCHICAL MODELING

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QUALITY MODELS

View model• Transcendental view• User view• Manufacturing view• Product view• Value-based view

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Transcendental view Quality is something that can be recognized through

experience, but not defined in some tractable form. A good quality object stands out, and it is easily recognized.

User view Quality concerns the extent to which a product meets user

needs and expectations. Is a product fit for use? This view is highly personalized.

A product is of good quality if it satisfies a large number of users. It is useful to identify the product attributes which the users consider

to be important. This view may encompass many subject elements, such as

usability, reliability, and efficiency.

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Manufacturing view This view has its genesis in the manufacturing industry – auto and

electronics. Key idea: Does a product satisfy the requirements?

Any deviation from the requirements is seen as reducing the quality of the product.

The concept of process plays a key role. Products are manufactured “right the first time” so that the cost is

reduced Development cost Maintenance cost

Conformance to requirements leads to uniformity in products. Some argue that such uniformity does not guarantee quality. Product quality can be incrementally improved by improving the

process. The CMM and ISO 9001 models are based on the manufacturing view

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Product view Hypothesis: If a product is manufactured with good internal

properties, then it will have good external properties. One can explore the causal relationship between internal

properties and external qualities. Example: Modularity enables testability.

Value-based view This represents the merger of two concepts: excellence and worth. Quality is a measure of excellence, and value is a measure of

worth. Central idea

How much a customer is willing to pay for a certain level of quality. Quality is meaningless if a product does not make economic sense. The value-based view makes a trade-off between cost and quality.

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QUALITY CRITERIA AND ITS INTERRELATION

SOFTWARE QUALITY ASSURANCE An alternate view of Quality:

is not absolute is multidimensional, can be difficult to quantify has aspects that are not easy to measure assessment is subject to constraints (e.g., cost) is about acceptable compromises criteria are not independent, can conflict

SOFTWARE QUALITY ASSURANCE Quality Criteria include:

correctness efficiency flexibility integrity interoperability maintainability portability reliability reusability testability usability

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MCCALL’S QUALITY FACTORS AND CRITERIA

Q

uality Factors

McC

all, Richards, and W

alters studied the concept of softw

are quality in terms of tw

o key concepts as follow

s:quality factors, and

quality criteria.

A quality factor represents the behavioral

characteristic of a system.

Exam

ples: correctness, reliability, efficiency, testability, portability, …

A quality criterion is an attribute of a quality

factor that is related to software

development.

Exam

ple:

Modularity is an attribute of the architecture

of a software system

.

A highly m

odular software allow

s designers to put cohesive com

ponents in one module,

thereby increasing the maintainability of the

system.

McC

all et al. identified 11 quality factors (Table 17.1.)

37

MCCALL’S QUALITY FACTORS AND CRITERIA

38

MCCALL’S QUALITY FACTORS AND CRITERIA

The 11 quality factors defined in

Table 17.1 have been grouped into three broad categories (S

ee Table 17.2.)

Product operation

Product revision

Product transition

Table 17.2: Categorization of M

cCall’s

quality factors [10].

39

MCCALL’S QUALITY FACTORS AND CRITERIA

Quality C

riteria

A quality criterion is an attribute of a

quality factor that is related to softw

are development.

Exam

ple:

Modularity is an attribute of the

architecture of a software system

.

A highly m

odular software allow

s designers to put cohesive com

ponents in one m

odule, thereby increasing the m

aintainability of the system.

In Table 17.3, we have listed 23

quality criteria.

SE, Quality, Hans van Vliet, ©2008 40

QUALITY ATTRIBUTES (MCCALL)

Product operation Correctness does it do what I want? Reliability does it do it accurately all

of the time? Efficiency will it run on my

hardware as well as it can? Integrity is it secure? Usability can I use it?

Product revision Maintainability can I fix it? Testability can I test it? Flexibility can I change it?

Product transition Portability will I be able to use it on

another machine? Reusability will I be able to reuse

some of the software? Interoperability will I be able to interface it with another

system?

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MCCALL’S QUALITY FACTORS AND CRITERIA

Table 17.3: McC

all’s quality criteria [10].

42

MCCALL’S QUALITY FACTORS AND CRITERIA

Relationship B

etween Q

uality F

actors and Quality C

riteriaE

ach quality factor is positively influenced by a set of quality criteria, and the sam

e quality criterion im

pacts a number of quality factors.

Exam

ple: Simplicity im

pacts reliability, usability, and testability.

If an effort is made to im

prove one quality factor, another quality factor m

ay be degraded.

Portable code may be less efficient.

Som

e quality factors positively im

pact others.

An effort to im

prove the correctness of a system

will increase its reliability.

See F

igure 17.1.

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MCCALL’S QUALITY FACTORS AND CRITERIA

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THE ISO 9126 QUALITY CHARACTERISTICS

The IS

O 9126 docum

ent is the product of an international effort.

ISO: International O

rganization for S

tandardization

The docum

ent defines six broad quality characteristics as show

n in Table 17.4.

The docum

ent includes an example

quality model (F

igure 17.2) that further decom

poses the quality characteristics.

Figure 17.2 is just an exam

ple, and not a universal one.

The 20 subcharacteristics of F

igure 17.2 have been defined in Table 17.5.

45

THE ISO 9126 QUALITY CHARACTERISTICS

Table 17.4: ISO

9126 quality characteristics.

46

THE ISO 9126 QUALITY CHARACTERISTICS

47

THE ISO 9126 QUALITY CHARACTERISTICS

48

THE ISO 9126 QUALITY CHARACTERISTICS

McC

all’s quality model vs. IS

O 9126 m

odel

What is called quality factor in M

cCall’s m

odel is called a quality subcharacteristic in the IS

O

9126 model.

T

he following quality factors/characteristics are

found in both the models.

reliability, usability, efficiency, maintainability, and

portability

Differences betw

een the two m

odels

The IS

O 9126 m

odel emphasizes on characteristics

visible to the users, whereas the M

cCall m

odel considers internal qualities as w

ell.

In McC

all’s model, one quality criterion can im

pact m

any quality factors, whereas in the IS

O 9126

model, one subcharacteristic im

pacts exactly one quality characteristic.

A high-level quality factor, such as testability, in the

McC

all’s model is a low

-level subcharacteristic of m

aintainability in the ISO

9126 model.

Concerns

There is no consensus about w

hat high-level quality factors are m

ost important at the top

level. McC

all, et al. define 11 high-level quality factors, w

hereas there are only six in the ISO

9126 docum

ent.

There is no consensus regarding w

hat is a top-level quality factor/ characteristic and w

hat is a m

ore concrete quality criterion/ subcharacteristic.

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

T

he international organization ISO

has developed a series of standards for quality assurance and quality m

anagement, collectively know

n as the IS

O 9000.

The IS

O 9000 standards are

reviewed and updated once every 5-

8 years. The standards released in

the year 2000 are known as IS

O

9000:2000.

There are three com

ponents of the IS

O 9000:2000 standard.

ISO

9000: Fundam

entals and vocabulary

ISO

9001: Requirem

ents

ISO

9004: Guidelines for perform

ance im

provements

Note: IS

O 9002 and IS

O 9003 w

ere parts of IS

O 9000:1994, but these

are no more parts of IS

O 9000:2000.

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

ISO

9000:2000 Fundam

entals:

This is based on eight principles.

Principle 1: Custom

er focusPrinciple 2: L

eadershipPrinciple 3: Involvem

ent of people

Principle 4: Process approach

Principle 5: System approach to

managem

ent

Principle 6: Continual im

provement

Principle 7: Factual approach to decision m

aking

Principle 8: Mutually beneficial supplier

relationships

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

ISO

9001:2000 Requirem

ents

The five m

ajor parts of this document

are as follows.

Part 4. Systemic requirem

entsPart 5. M

anagement requirem

ents

Part 6. Resource requirem

ents

Part 7. Realization requirem

ents

Part 8. Rem

edial requirements

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

ISO

9001:2000 Requirem

ents

Part 4. S

ystemic requirem

ents (partial)

Docum

ent the organizational policies and goals. P

ublish a vision document.

Docum

ent all quality processes and their interrelationship.

Implem

ent a mechanism

to approve docum

ents before those are distributed.

Part 5: M

anagement requirem

ents (partial)

Generate an aw

areness for quality to m

eet a variety of requirements, such as

customer, regulatory, and statutory.

Focus on customers by identifying and

meeting their requirem

ents in order to satisfy them

.

Develop a quality policy to m

eet the custom

er’s needs.

Clearly define individual responsibilities

and authorities concerning the im

plementation of quality policies.

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

ISO

9001:2000 Requirem

ents

Part 6. R

esource requirements

(partial)Identify and provide resources required

to support the organizational quality policy in order to realize the quality objectives.

Allocate quality personnel resource to

projects.

Put in place a mechanism

to enhance the quality level of personnel.

Part 7: R

ealization requirements

(partial)

Develop a plan to realize a product from

its requirem

ents.

Interact with custom

ers to gather their requirem

ents. Classify those

requirements.

Review

the requirements.

Follow a defined purchasing process by

evaluating potential suppliers based on a num

ber of factors, such as ability to m

eet requirements and price.

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THE ISO 9000:2000 SOFTWARE QUALITY STANDARD

ISO

9001:2000 Requirem

ents

Part 8. R

emedial requirem

ents (partial)

Measure and track the custom

er’s satisfaction level.

Perform internal audit.

Exam

ple: Find out whether or not

personnel with adequate education,

experience, and skill have been assigned to a project.

Monitor processes by using a set of key

performance indicators.

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THANK YOU

For your time

For participation in the session

For being a learner

For the work you do everyday!!!!!!!

Contact:

4.seema@gmail.com