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Requirements Engineering. Quality Management. Software Quality Management. What is Quality in Software ? The end product should meet the specification Issues Bad or imperfect specification Non-functional requirements What is Quality Management ?

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requirements engineering

Requirements Engineering

Quality Management

software quality management
Software Quality Management
  • What is Quality in Software ?
    • The end product should meet the specification
    • Issues
      • Bad or imperfect specification
      • Non-functional requirements
  • What is Quality Management ?
    • Defining standards and policies to be followed in development
    • Checking to see that they are followed
    • In addition, develop a quality culture
  • Functions of Quality Management
    • Quality Assurance – establishing the frame work
    • Quality Planning – the use of the framework in planning specific projects
    • Quality Control – The process by which compliance with the standards and processes is ensured
software quality
Software Quality
  • Quality Management is a separate process
    • Needs independence
      • From budget
      • From schedule
      • From project management chain
      • From Product Development Groups
    • ISO 9000 a guide to quality process
      • ISO 9001 general applicability to product development
      • ISO 9000-3 interprets ISO 9000 for software development
    • Deliverables from the software process are submitted to QC for review
iso 9000 and quality
ISO 9000 and Quality
  • ISO 9000 supplies Quality Models
    • Subset developed as Organizational quality manual
      • which documents the organization quality process
    • The subset is the basis used to develop project quality plan
    • Project quality management uses the plan to enforce the organizational standards
    • See text for references to ISO materials
iso 9001 2000 standard
ISO 9001:2000 Standard
  • ISO 9001:2000 is the quality assurance standard that applies to software engineering.
  • The standard contains 20 requirements that must be present for an effective quality assurance system.
  • The requirements delineated by ISO 9001:2000 address topics such as
    • management responsibility, quality system, contract review, design control, document and data control, product identification and traceability, process control, inspection and testing, corrective and preventive action, control of quality records, internal quality audits, training, servicing, and statistical techniques.
quality assurance and standards
Quality assurance and standards
  • QA – defines the framework for achieving quality software
    • Defines the standards
      • Product
      • Process
    • Provide
      • Best practices - make the success of others available
      • Provides a checklist to judge if standards have been followed
      • Continuity – institutional memory
      • Sources
        • IEEE
        • ANSI
        • US DoD
        • NATO
basic definitions
Basic definitions
  • A failure is an unacceptable behaviour exhibited by a system
    • The frequency of failures measures the reliability
    • An important design objective is to achieve a very low failure rate and hence high reliability.
    • A failure can result from a violation of an explicit or implicit requirement
  • A defect is a flaw in any aspect of the system that contributes, or may potentially contribute, to the occurrence of one or more failures
    • It might take several defects to cause a particular failure
  • An error is a slip-up or inappropriate decision by a software developer that leads to the introduction of a defect
effective and efficient testing
Effective and Efficient Testing
  • To test effectively, you must use a strategy that uncovers as many defects as possible.
  • To test efficiently, you must find the largest possible number of defects using the fewest possible tests
    • Testing is like detective work:
      • The tester must try to understand how programmers and designers think, so as to better find defects.
      • The tester must not leave anything uncovered, and must be suspicious of everything.
      • It does not pay to take an excessive amount of time; tester has to be efficient.
  • Documents require standards for
    • Process – production i.e. Creation thru print final
    • Documents - structure and presentation
      • Identification
      • Structure
      • Presentation – font, styles, logos, etc.
      • Update – version control
    • Interchange – exchange compatibility
  • Process
    • How do we improve quality in the product
      • Feedback
      • Standardization
quality planning and control
Quality Planning and Control
  • Plan
    • Developed early
    • Addresses the most important software quality attributes
      • Safety
      • Security
      • Reliability
      • Etc.
  • Control
    • Quality reviews
      • Design or program inspection – errors in requirements, design or code
      • Progress reviews – schedule, budget
      • Quality the whole package
measurement and metrics
Measurement and Metrics
  • Metrics
    • Not widely used in software industry
      • Lack of standards
      • Lack of standard processes
    • Control – measures associated with process
      • Time to repair defects
      • Time to modify or enhance
    • Predictor – associated with the product
      • Cyclomatic count
      • Fog factor
      • Size
  • Measurement process
    • Choose measurements –
    • Select components
    • Measure
    • Identify anomalous measurements
    • Analyze components
product metrics
Product Metrics
  • Product Metrics
    • Concerned with the software itself
      • Dynamic – measurements made during execution
      • Static – made of the representations
        • Design
        • Program
        • Documentation
    • Dynamic assess
      • Efficiency
      • Reliability
      • Relatively easy to measure
    • Static
      • Complexity
      • Understandability
      • Maintainability
defect testing
Defect testing
  • Goal – expose latent defects in the system before it is implemented (delivered)
    • Successful test causes the system to perform incorrectly
    • Demonstrates the presence of program faults
  • Test case
    • Specifications of input and output
    • Statement of what is being tested
  • Test data
    • Inputs devised to test the code.
  • Test thoroughness
    • Exhaustive not possible
    • Policies of the organization not the development team
documentation defects
Documentation defects
  • Defect:
    • The software has a defect if the user manual, reference manual or on-line help:
      • gives incorrect information
      • fails to give information relevant to a problem.
  • Testing strategy:
    • Examine all the end-user documentation, making sure it is correct.
    • Work through the use cases, making sure that each of them is adequately explained to the user.
writing formal test cases and test plans
Writing Formal Test Cases and Test Plans
  • A test case is an explicit set of instructions designed to detect a particular class of defect in a software system.
    • A test case can give rise to many tests.
    • Each test is a particular running of the test case on a particular version of the system.
test plans
Test plans
  • A test plan is a document that contains a complete set of test cases for a system
      • Along with other information about the testing process.
    • The test plan is one of the standard forms of documentation.
    • If a project does not have a test plan:
      • Testing will inevitably be done in an ad-hoc manner.
      • Leading to poor quality software.
    • The test plan should be written long before the testing starts.
    • You can start to develop the test plan once you have developed the requirements.
information to include in a formal test case
Information to include in a formal test case

A. Identification and classification:

  • Each test case should have a number, and may also be given a descriptive title.
  • The system, subsystem or module being tested should also be clearly indicated.
  • The importance of the test case should be indicated.

B. Instructions:

  • Tell the tester exactly what to do.
  • The tester should not normally have to refer to any documentation in order to execute the instructions.

C. Expected result:

  • Tells the tester what the system should do in response to the instructions.
  • The tester reports a failure if the expected result is not encountered.

D. Cleanup (when needed):

  • Tells the tester how to make the system go ‘back to normal’ or shut down after the test.
levels of importance of test cases
Levels of importance of test cases
  • Level 1:
    • First pass critical test cases.
    • Designed to verify the system runs and is safe.
    • No further testing is possible.
  • Level 2:
    • General test cases.
    • Verify that day-to-day functions correctly.
    • Still permit testing of other aspects of the system.
  • Level 3:
    • Detailed test cases.
    • Test requirements that are of lesser importance.
    • The system functions most of the time but has not yet met quality objectives.
determining test cases by enumerating attributes
Determining test cases by enumerating attributes
  • It is important that the test cases test every aspect of the requirements.
    • Each detail in the requirements is called an attribute.
      • An attribute can be thought of as something that is testable.
      • A good first step when creating a set of test cases is to enumerate the attributes.
      • A way to enumerate attributes is to circle all the important points in the requirements document.
    • However there are often many attributes that are implicit.
software inspections
Software Inspections
  • Software Inspections
    • Program inspections
      • 1970’s
      • Line by line code review
      • Defect detection not enhancement
      • Team of four to six usually
        • Author
        • Reader
        • Tester
        • Moderator
          • Maybe scribe and chief moderator
      • Requires
        • Precise spec
        • Members familiar with standards
        • Up to date set of code
      • About 2 hours
reviews inspections
Reviews & Inspections

... there is no particular reason

why your friend and colleague

cannot also be your sternest critic.

Jerry Weinberg

what are reviews
What Are Reviews?
  • a meeting conducted by technical people for technical people
  • a technical assessment of a work product created during the software engineering process
  • a software quality assurance mechanism
  • a training ground
what reviews are not
What Reviews Are Not
  • A project summary or progress assessment
  • A meeting intended solely to impart information
  • A mechanism for political or personal reprisal!
the players
The Players



standards bearer (SQA)






user rep

conducting the review
Conducting the Review

be prepared—evaluate


product before the review

review the product, not


the producer

keep your tone mild, ask


questions instead of

making accusations

stick to the review agenda



raise issues, don't resolve them


avoid discussions of style—stick to technical



schedule reviews as project tasks


record and report all review results

sample driven reviews sdrs
Sample-Driven Reviews (SDRs)
  • SDRs attempt to quantify those work products that are primary targets for full FTRs.

To accomplish this …

  • Inspect a fraction ai of each software work product, i. Record the number of faults, fi found within ai.
  • Develop a gross estimate of the number of faults within work product i by multiplying fi by 1/ai.
  • Sort the work products in descending order according to the gross estimate of the number of faults in each.
  • Focus available review resources on those work products that have the highest estimated number of faults.
metrics derived from reviews
Metrics Derived from Reviews

inspection time per page of documentation

inspection time per KLOC or FP (or Use Case)

inspection effort per KLOC or FP (or Use Case)

errors uncovered per reviewer hour

errors uncovered per preparation hour

errors uncovered per SE task (e.g., requirements)

number of minor errors (e.g., typos)

number of major errors

(e.g., nonconformance to User wants/needs vision)

number of errors found during preparation

statistical sqa
Statistical SQA


& Process

Collect information on all defects

Find the causes of the defects

Move to provide fixes for the process


... an understanding of how

to improve quality ...

six sigma for software engineering
Six-Sigma for Software Engineering
  • The term “six sigma” is derived from six standard deviations—3.4 instances (defects) per million occurrences — implying an extremely high quality standard.
  • The Six Sigma methodology defines these core steps:
    • Definecustomer requirements and deliverables and project goals via well-defined methods of customer communication
    • Measure the existing process and its output to determine current quality performance (collect defect metrics)
    • Analyzedefect metrics and determine the vital few causes.
    • Improve the process by eliminating the root causes of defects.
    • Controlthe process to ensure that future work does not reintroduce the causes of defects.
inspecting compared to testing
Inspecting compared to testing
  • Both testing and inspection rely on different aspects of human intelligence.
  • Testing can find defects whose consequences are obvious but which are buried in complex code.
  • Inspecting can find defects that relate to maintainability or efficiency.
  • The chances of mistakes are reduced if both activities are performed.
testing or inspecting which comes first
Testing or inspecting, which comes first?
  • It is important to inspect software before extensively testing it.
  • The reason for this is that inspecting allows you to quickly get rid of many defects.
  • If you test first, and inspectors recommend that redesign is needed, the testing work has been wasted.
    • There is a growing consensus that it is most efficient to inspect software before any testing is done.
  • Even before developer testing
quality assurance in general
Quality Assurance in General
  • Root cause analysis
    • Determine whether problems are caused by such factors as
      • Lack of training
      • Schedules that are too tight
      • Building on poor designs or reusable technology
measure quality and strive for continual improvement
Measure quality and strive for continual improvement
  • Things you can measure regarding the quality of a software product, and indirectly of the quality of the process
    • The number of failures encountered by users.
    • The number of failures found when testing a product.
    • The number of defects found when inspecting a product.
    • The percentage of code that is reused.
      • More is better, but don’t count clones.
    • The number of questions posed by users to the help desk.
      • As a measure of usability and the quality of documentation.
post mortem analysis
Post-mortem analysis
  • Looking back at a project after it is complete, or after a release,
    • You look at the design and the development process
    • Identify those aspects which, with benefit of hindsight, you could have done better
    • You make plans to do better next time

Meaning of “V&V” (Boehm)


are we buildingthe thing right?


are we buildingthe right thing?

Graphics reproduced with permission from Corel.

process standards
Process standards
  • The personal software process (PSP):
    • Defines a disciplined approach that a developer can use to improve the quality and efficiency of his or her personal work.
    • One of the key tenets is personally inspecting your own work.
  • The team software process (TSP):
    • Describes how teams of software engineers can work together effectively.
  • The software capability maturity model (CMM):
    • Contains five levels, Organizations start in level 1, and as their processes become better they can move up towards level 5.
  • ISO 9000-2:
    • An international standard that lists a large number of things an organization should do to improve their overall software process.
the psp evolution humphrey


Cyclic development

1000’s of lines

The PSP Evolution (Humphrey)

Skills added

to prior stage


Design templates


Code reviews

Design reviews

100’s of lines


capability at the same level


Task planning

Schedule planning


Size estimation

Test report


Coding standards

Process improvement proposal

Size measurement


Current personal process

Basic measurements

(Adapted from [Hu1] )

tsp objectives 1 humphrey
TSP Objectives 1 (Humphrey)
  • Build self-directed teams
    • 3-20 engineers
    • establish own goals
    • establish own process and plans
    • track work
  • Show managers how to manage teams
    • coach
    • motivate
    • sustain peak performance

Graphics reproduced with permission from Corel.

tsp objectives 2 humphrey
TSP Objectives 2 (Humphrey)
  • Accelerate CMM improvement
    • make CMM 5 “normal”
  • “Provide improvement guidelines to high-maturity organizations”
  • “Facilitate university teaching of industrial-grade teams”
background capability maturity model for software
Background - Capability Maturity Model for Software
  • 1986 Software Engineering Institute, and the Mitre Corp. begin to develop a process maturity framework to improve software processes
  • 1987 description of the framework
    • Assessment
    • Evaluation
  • 1991 evolved to the Capability Maturity Model for Software (CMM v1.0)
    • Recommended practices in key process areas (KPA’s)
    • Gain control of processes for developing and maintaining software
    • Evolve to a culture of software engineering and management excellence
  • Current
what is the cmm
What is the CMM?
  • Concept:
    • The application of process management and quality improvement concepts to software development and maintenance
  • Model:
    • A model for organizational improvement
  • Guidelines:
    • A guide for evolving toward a culture of engineering excellence
  • Basis for Measurement:
    • The underlying structure for reliable and consistent software process assessments, software capability evaluations, and interim profiles
maturity levels are a framework for process improvement
Maturity Levels are a Framework for Process Improvement
  • Based on Continuous Process Improvement:
    • based on many small, evolutionary steps rather than revolutionary innovations.
  • Plateau:
    • A maturity level is a well-defined evolutionary plateau toward achieving a mature software process.
  • Foundation:
    • Each maturity level provides a layer in the foundation for continuous process improvement.
  • Priority Order:
    • The levels also help an organization prioritize its improvement efforts.
symptoms of process failure
Symptoms of Process Failure
  • Commitments consistently missed

• Late delivery

• Last minute crunches

• Spiraling costs

  • No management visibility into progress

• You’re always being surprised.

  • Quality problems

• Too much rework

• Functions do not work correctly.

• Customer complaints after delivery

  • Poor morale
    • • People frustrated
    • • Is anyone in charge?
settling for less
Settling for Less
  • Do these statements sound familiar? If they do, your

organization may be settling for less than it is capable of

and may be a good candidate for process improvement.

    • a senior software manager (industry)

“I'd rather have it wrong than have it late. We can always

fix it later.”

    • a program manager (government)

“The bottom line is schedule. My promotions and raises are based on meeting schedule first and foremost.”


the process management premise
The Process Management Premise
  • The quality of a system is highly influenced by

the quality of the process used to acquire, develop,

and maintain it.

  • This premise implies a focus on processes as well

as on products.

• This is a long-established premise in manufacturing

(and is based on TQM principles as taught by Shewhart,

Juran, Deming, and Humphrey).

• Belief in this premise is visible worldwide in quality

movements in manufacturing and service industries

(e.g., ISO standards).

cmm software overview
CMM (Software) Overview

SEI’s Vision:To bring engineering discipline to the development and maintenance of software products

Desired Result:Higher quality -- better products for a better pricePredictability -- function/quality, on time, within budget

Methodology to Achieve that Desired Result:

2. Identify Desired State:Understand the description of the next Level

1. Identify Current State:Know your current Capability Maturity Level

3. Reduce the Gap:Plan, implement, and institutionalizethe key practices of the next Level.Repeat until continuous optimization is part of the culture.

assessment vs evaluation
Assessment vs Evaluation
  • A software process assessment is an appraisal by a trained team of software professionals to determine
    • the state of an organization's current software process,
    • the high-priority software process-related issues facing an organization,
    • and to obtain the organizational support for software process improvement.
  • A software capability evaluation is an appraisal by a trained team of professionals to identify contractors who are qualified to perform the software work or to monitor the state of the software process used on an existing software effort.
a foundation not a destination
A Foundation, Not a Destination
  • The optimizing level (Level 5) is not the destination of process management.
  • The destination is better products for a better price: economic survival
  • The optimizing level is a foundation for building an ever-improvingcapability.
fundamental concepts underlying process maturity
Fundamental Concepts Underlying Process Maturity

A software process

can be defined as a set of activities, methods, practices, and transformations that people use to develop and maintain software and the associated products (e.g., project plans, design documents, code, test cases, and user manuals). As an organization matures, the software process becomes better defined and more consistently implemented throughout the organization.

Software process capability

describes the range of expected results that can be achieved by following a software process. The software process capability of an organization provides one means of predicting the most likely outcomes to be expected from the next software project the organization undertakes.

Software process performance

represents the actual results achieved by following a software process. Thus, software process performance focuses on the results achieved, while software process capability focuses on results expected.

Software process maturity

is the extent to which a specific process is explicitly defined, managed, measured, controlled, and effective. Maturity implies a potential for growth in capability and indicates both the richness of an organization's software process and the consistency with which it is applied in projects throughout the organization.

fundamental concepts underlying process maturity52
Fundamental Concepts Underlying Process Maturity

Maturity Level

A well-defined evolutionary plateau toward achieving a mature software process. Each maturity level comprises a set of process goals that, when satisfied, stabilize an important component of the software process. Achieving each level of the maturity framework establishes a different component in the software process, resulting in an increase in the process capability of the organization.


As a software organization gains in software process maturity, it institutionalizes it software process via policies, standards, and organizational structures. Institutionalization entails building an infrastructure and a corporate culture that supports the methods, practices, and procedures of the business so that they endure after those who originally defined them have gone.

the five levels of software process maturity
The Five Levels of Software Process Maturity

Continuously Improving Process


Focus on process improvement

4. Managed

Predictable Process

Managing Change

Process measured and controlled

Standard, Consistent Process

3. Defined

Product and Process Quality

Process characterized, fairly well understood

2. Repeatable

Disciplined Process

Integrated Engineering Process

Can repeat previously mastered tasks

1. Initial

Project Management

Unpredictable and poorly controlled

part 2 cmm level 2 key process areas
Part 2. CMM Level 2 Key ProcessAreas

Software Quality Assurance

Requirements Management


Software Configuration Management

SoftwareProject Tracking and Oversight

Software Subcontract Management

cmm level 3 key process areas
CMM Level 3 Key Process Areas

Organization Process Focus

Organization Process Definition

Training Program

Intergroup Coordination


Integrated Software Management

Software Product Engineering

understanding the repeatable and defined levels 2 3
Understanding the Repeatable and DefinedLevels (2 & 3)
  • To achieve Level 2, management must focus on its own processes to achieve a disciplined software process and establish a leadership position.
  • Level 2 provides the foundation for Level 3 because the focus is on management acting to improve its processes before tackling technical and organizational issues at Level 3.
  • Processes may differ between projects in a Level 2 organization; the organizational requirement for achieving Level 2 is that there are policies that guide the projects in establishing the appropriate management processes.
  • Documented procedures provide the foundation for consistent processes that can be institutionalized across the organization, with training and assurance.
  • Level 3 builds on this project management foundation by defining, integrating, and documenting the entire software process.
comparison of level 2 and level 3
Comparison of Level 2 and Level 3
  • Difference between Level 1 and Level 2:
    • Level 1
      • is ad hoc and occasionally chaotic; few processes are defined, and success depends on individual effort.
    • Level 2:
      • Basic project management processes are established to track cost, schedule, and functionality.
      • The necessary process discipline is in place to repeat earlier successes on projects with similar applications.
  • Difference between Level 2 and Level 3:Level 3 encompasses integrated and standardized management and engineering activities; projects tailor the organization’s standard software process to meet their needs.

The CMM Structure

Maturity Levels




Key Process Areas



Organized by

Common Features


Implementation orinstitutionalization


Key Practices


Infrastructure orActivities


Note 5. The process of going back and forth between doing changes in the design

followed by a code generation and then doing changes in the code followed

by a reverse engineering for every change, the best possible perspective,

is called Round-trip Engineering.