Quality Concepts

by Ronni Kahalani, Copenhagen School of Design & Technology.

With inspiration from the book Software Engineering - A Practitioner's Approach.

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Principles, concepts, and techniques that are applied

to manage and control software quality.

Who am I?

Thank you for stopping by.

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I’m Ronni. I hope you’re well and wish you a safe and worthy journey.

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This presentation is part of the Software Engineering Series, from my lectures at Copenhagen School of Design & Technology.

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You can view the Introducing Myself, if you want to know a little more about who I am.

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All my presentations and materials are free and available at my blog post: Software Engineering.

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Don’t let me uphold you,

continue your journey, go to next slide.

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Agenda

• Intro
• Quick Look
• What Is Quality?
• Software Quality
• The Software Quality Dilemma
• Achieving Software Quality
• Summary

Intro

Learn about the principles, concepts, and techniques that are applied to manage and control software quality.

• Generic characteristics of high-quality software
• Conduct effective quality reviews
• Software quality assurance
• Strategies for software testing
• Methods to design effective test cases
• Manage and control changes
• Measures and metrics assess the quality

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Intro

By the 1990s, major corporations recognized that billions of dollars each year were being wasted on software that didn't deliver the features and functionality that were promised.

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• Major software fault might cripple important infrastructure, costing tens of billions more
• Plagues nearly every organization that uses computers
• Causing lost work hours during computer downtime
• Lost or corrupted data
• Missed sales opportunities
• High IT support- and maintenance costs
• Low customer satisfaction

Intro

Experts say…

• Only 3 or 4 defects per 1,000 lines of code to make a program perform poorly.
• Most programmers inject about 1 error for every 10 lines of code 
• Multiply that by the millions of lines of code in many commercial products
• It costs software vendors at least half their development budgets to fix errors while testing

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Get the picture? 

Intro

Who is to blame?

• Customers blame developers, arguing that sloppy practices lead to low-quality software.
• Developers blame customers (and other stakeholders ), arguing that irrational delivery dates and a continuing stream of changes force them to deliver software before it has been fully validated

Who's right?

Both -and that's the problem ☹

Quick Look

• What is it?
• You know quality when you see it
• It can be an elusive thing to define
• Quality is something we have to define
• Who does it?
• Everyone involved in the software process is responsible for quality
• Why is it important?
• Do it right, or do it over again
• Results in lower costs, and more importantly, improved time to market

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Quick Look

• What are the steps?
• Proven software engineering process and practice
• Solid project management
• Comprehensive quality control
• Presence of a quality assurance infrastructure
• What is the work product? 
• Software that meets its customer's needs
• Provides value to all who use it
• How do I ensure that I've done it right?
• Examining the results of all quality control activities
• Measure quality by examining errors before delivery and defects released to the field

What Is Quality?

You know what it is, yet you don't know what it is…

What Is Quality?

• You know what it is, yet you don't know what it is…
• If you can't say what Quality is…How do you know what it is? Does it even exists?

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But for all practical purposes it really does exist!

“Quality is a complex and multifaceted concept" �which can be described from 5 different points of view. 

- by David Garvin of the Harvard Business School

What Is Quality? - David Garvin’s 5 Views

• Transcendental view
• User view
• Manufacturer's view
• Product view
• Value-based view

What Is Quality? - David Garvin’s 5 Views

Transcendental view

• Something you immediately recognize, but cannot explicitly define.

User view

• If a product meets an end user's specific goals.

Manufacturer's view

• If the product conforms original specification.

Product view

• Can be tied to inherent characteristics (e.g. functions and features) of a product.

Value-based view

• Measures on how much a customer is willing to pay for a product.

What Is Quality?

In reality, quality encompasses all of these views and more…

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“Quality is important, but if the user isn't satisfied, nothing else really matters.”

• by Robert Glass

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Argues that a more "intuitive" relationship is in order:

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user satisfaction = 

compliant product + good quality + delivery within budget and schedule 

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"A product's quality is a function of how much it changes the world for the better.“

- by DeMarco

Software Quality

How do we define software quality?

Software Quality

How do we define software quality?

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In the most general sense:

”An effective software process applied in a manner�that creates a useful product that provides�measurable value for those who produce it �and those who use it”

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Could be modified or extended and debated endlessly…

Software Quality

3 important points:

• An effective software process establishes the infrastructure that supports any effort at building a high-quality software product.
• A useful product delivers the content, functions, and features that the end user desires, but as important, it delivers these assets in a reliable, error-free way.
• By adding value for both the producer and user of a software product, high-quality software provides benefits for the software organization and the end-user community.

Garvin's Quality Dimensions

Although Garvin's 8 dimensions of quality were not developed specifically for software, they can be applied when software quality is considered.

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Garvin's quality dimensions provide you with a "soft" look at software quality.

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You also need a set of "hard" quality factors:

• Factors that can be directly measured.
• Factors that can be measured only indirectly.

Garvin's Quality Dimensions

Garvin's 8 dimensions of quality:

• Performance quality
• Feature quality
• Reliability
• Conformance
• Durability
• Serviceability
• Aesthetics
• Perception

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McCall’s Quality Factors

McCall, Richards, and Walters propose a useful categorization of factors that affect software quality.

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Focus on 3 important aspects of a software product:

1. Its operational characteristics
2. Its ability to undergo change
3. Its adaptability to new environments

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Many of the metrics can be measured only indirectly.

McCall’s Quality Factors

ISO 9126 Quality Factors

The standard identifies 6 key quality attributes developed in an attempt to identify the key quality attributes for computer software:

• Functionality
• Reliability
• Usability
• Efficiency
• Maintainability
• Portability

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Provides a worthwhile basis for indirect measures and an excellent checklist for assessing the quality of a system.

ISO 25010 - Systems and software engineering

• Quality in Use Model
• Effectiveness
• Efficiency
• Satisfaction
• Freedom from Risk
• Context Coverage
• Product Quality
• Functional Suitability
• Performance Efficiency
• Compability
• Usability
• Reliability
• Security
• Maintainability
• Portability

https://www.iso.org/standard/78175.html

Targeted Quality Factors

• The quality dimensions and factors presented focus on the software as a whole and can be used as a generic indication of the quality of an application.

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• A software team can develop a set of quality characteristics and associated questions that would probe the degree to which each factor has been satisfied.

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To conduct your assessment, you’ll need to address specific, measurable (or at least, recognizable) attributes of the interface.

Intuitiveness–Efficiency–

Robustness–Richness

Intuitiveness – Efficiency – Robustness – Richness

Intuitiveness. The degree to which the interface follows expected usage patterns so that even a novice can use it without significant training.

• Is the interface layout conducive to easy understanding?
• Are interface operations easy to locate and initiate?
• Does the interface use a recognizable metaphor?
• Is input specified to economize keystrokes or mouse clicks?
• Does the interface follow the three golden rules? Link
• Does aesthetics aid in understanding and usage?

Intuitiveness – Efficiency – Robustness – Richness

Efficiency. The degree to which operations and information can be located or initiated.

• Does the interface layout and style allow a user to locate operations and information efficiently?
• Can a sequence of operations (or data input) be performed with an economy of motion?
• Are output data or content presented so that it is understood immediately?
• Have hierarchical operations been organized in a way that minimizes the depth to which a user must navigate to get something done? 

Intuitiveness – Efficiency – Robustness – Richness

Robustness. The degree to which the software handles bad input data or inappropriate user interaction.

• Will the software recognize the error if data values are at or just outside prescribed input boundaries?�More importantly, will the software continue to operate without failure or degradation?
• Will the interface recognize common cognitive or manipulative mistakes and explicitly guide the user back on the right track?
• Does the interface provide useful diagnosis and guidance when an error condition (associated with software functionality) is uncovered?

Intuitiveness – Efficiency – Robustness – Richness

Richness. The degree to which the interface provides a rich feature set.

• Can the interface be customized to the specific needs of a user?
• Does the interface provide a macro capability that enables a user to identify a sequence of common operations with a single action or command?

The Software Quality Dilemma

What is "good enough"?

The Software Quality Dilemma

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Bertrand Meyer discusses what is called the quality dilemma...

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…people in industry try to get to that magical middle ground where

the product is good enough not to be rejected right away, such as during evaluation,

but also not the object of so much perfectionism and so much work that it would take too long or cost too much to complete. 

"Good Enough" Software

Accept the argument made by Meyer…

“Is it acceptable to produce "good enough" software?”

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The answer to this question must be yes.

• Major software companies does it every day.
• Some of the functions and features delivered in Version 1.0 may not be of the highest quality and plan for improvements in Version 2.0

"Good Enough" Software

What is "good enough"?

It is true that "good enough" may work in some application domains and for a few major software companies.

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But how about:

• Is “good enough” an option for small companies?
• Critical real -time software integrated with hardware (e .g., automotive, aviasion, telecoms software), delivering software with known bugs can be negligent and open your company to expensive litigation. In some cases, it can even be criminal.

The Cost of Quality

Which cost should we be worried about?

Relative cost of correcting errors and defects

The Cost of Quality

Quality has a cost, but lack of quality also has a cost.

• Which cost should we be worried about?

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Understand both…

• “The cost of quality” can be divided into costs associated with
• Prevention
• Appraisal
• Failure - Internal & External
• The cost of low-quality software

The Cost of Quality

• Prevention
• Management activities
• Technical activities
• Test planning
• All training associated with these activities
• Appraisal
• Technical reviews
• Data collection and metrics evaluation
• Testing and debugging

The Cost of Quality

• Failure – Internal (error)
• Perform rework (repair) to correct .
• When rework inadvertently generates side effects that must be mitigated.
• Collection of quality metrics that allow an organization to assess the modes of failure.
• Failure – External (defect), examples of costs:
• Complaint resolution.
• Product return and replacement.
• Help line support.
• Labour costs associated with warranty work.
• A poor reputation and the resulting loss of business.

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Bad things happen when low-quality software is produced ☹

The Cost of Quality

The relative costs to find and repair an error or defect increase dramatically as we go from prevention to detection to internal failure to external failure costs.

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According to industry average data:

• Correct a defect during code generation is approximately $977 per error.
• Correct the same error if it is discovered during system testing is $7,136 per error.

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Considers a large application that has 200 errors introduced during coding.

Risks

Downside of poorly designed and implemented applications does not always stop with dollars and time…

• Throughout the month of November 2000 at a hospital in Panama, 28 patients received massive overdoses of gamma rays during treatment for a variety of cancers.
• In the months that followed, 5 of these patients died from radiation poisoning and 15 others developed serious complications.�

What caused this tragedy?

• A software package, developed by a U.S. company, was modified by hospital technicians to compute modified doses of radiation for each patient.
• 3 Panamanian medical physicists, who tweaked the software to provide additional capability, were charged with second-degree murder.
• The US company was faced with serious litigation in two countries.

Poor quality leads to risks, some of them very serious.

Negligence and Liability

The story is all too common…the system might support:

• Corporate function, e.g. pension management
• Governmental function, e.g. healthcare administration or homeland security

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Work begins with the best of intentions on both sides…, by the time the system is delivered…

• Things have gone bad
• The system is late
• Fails to deliver desired features and functions
• Is error-prone
• Does not meet with customer approval

Litigation ensures…the “quality of the delivered system” comes into question.

Quality and Security

Stated simply,

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“Software that does not exhibit high quality, is easier to hack.”

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As a consequence, low-quality software can indirectly increase the security risk with all of its attendant costs and problems.

• To build secure systems, you focus on quality, and that focus begin during design.
• The earlier you find the software problem, the better.

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And there are 2 kinds of software problems:

• Bugs - Implementation problems.
• Software flaws - Architectural problems in the design.

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People pay too much attention to bugs and not enough on flaws.

The Impact of Management Actions

Software quality is often influenced as much by management decisions as it is by technology decisions.

• Estimation decisions
• If a delivery date is irrational, it is important to hold your ground. Explain why you need more time, or alternatively, suggest a subset of functionality that can be delivered (with high quality) in the time allotted.
• Scheduling decisions
• Quality suffers as a consequence, “A” may have defects that are hidden, only to be discovered much later.
• Risk-oriented decisions
• Our advice: taking the time to do it right is almost never the wrong decision.
• Have a way of handling things that do go wrong.

Achieving Software Quality

Software quality doesn't just appear.

Achieving Software Quality

Software quality doesn't just appear.

• It’s the result of good project management and solid software engineering practice
• Applied within the context of 4 broad activities:
• Software Engineering Methods
• Project Management Techniques
• Quality Control
• Quality Assurance

Software Engineering Methods

You must understand the problem to be solved.

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Use concepts and methods that can lead to a reasonably complete understanding of the problem and a comprehensive design that establishes a solid foundation for the construction activity.

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“If we can really understand the problem, the answer

will come out of it, because the answer is

not separate from the problem”

- by Jiddu Krishnamurti

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Project Management Techniques

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• Use estimation to verify that delivery dates are achievable.
• Schedule dependencies are understood and the team resists the temptation to use shortcuts.
• Risk planning is conducted.

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In addition, the project plan should include explicit techniques for quality and change management.

Machine Learning and Defect Prediction

Machine Learning / AI

• Learns and improves from experience, without being explicitly programmed.
• Access data and use it to learn from themselves.
• Automates the process of discovering predictive relationships between software metrics and defective components.

Defect Prediction

• Using a statistical techniques to examine the relationship among combinations of software metrics and software components containing known defects.
• Can reduce costs and development times.

A big part of what modern scientists do

Quality Control

Use actions to ensure each work product meets its quality goals:

• Models are reviewed
• Code should be inspected
• Testing steps are applied

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A combination of measurement and feedback that allows tuning the process.

Quality Assurance

Establish the infrastructure that supports:

• Solid software engineering methods
• Rational project management
• Quality control actions
• In addition, quality assurance consists of a set of auditing and reporting functions.

The goal of quality assurance: To provide management and technical staff with the data necessary to be informed about product quality.

If problems are identified: It is management's responsibility to address the problems and apply the necessary resources.

Summary

Every software organization is faced with the software quality dilemma.

Regardless of the approach that is chosen, quality does have a cost that can be discussed in terms of:

• Prevention
• All software engineering actions that are designed to prevent defects in the first place.
• Appraisal
• Are associated with those actions that assess software work products to determine their quality.
• Failure
• Encompass the internal price of failure and the external effects of poor quality.

Summary

Software quality is achieved through the application of:

• Software engineering methods.
• Solid management practices.
• Comprehensive quality control.

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All supported by a software quality assurance infrastructure.

Questions?

Anything? What’s on your mind? Come on ask me anything…

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