l 04 z quality engineering

8/9/2019 L 04 Z Quality Engineering

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Software Quality Assurance and Testing

(Section A)

Lecture 04

Software Quality Engineering


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Software Quality Engineering

Software Quality Engineering (SQE)

SQE Activities (described in the previous two lectures

) SQE in Software Process


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Software Quality Engineering Contd

What is Software Quality Engineering (SQE)?

Software Quality Engineering (SQE) is a process that

evaluates, assesses, and improves the quality of

software.

Typical Software Quality Attributes:

Reliability: ability of a program to achieve precisely its

intended mission

Robustness: ability of a program to react appropriately to

abnormal conditions

Efficiency: ability of a software to place as few demands as

possible on hardware resources, such as processor time,

memory space occupied, or network bandwidth, to achieve a

given task.


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Software Quality Engineering Contd

Typical Software Quality Attributes:

Maintainability: effort required modifying, updating, evolving,

or repairing a program during its operation.

Portability: effort required to transfer a program from one

computing environment or platform to another.

Reusability: ability and effort required to reuse a program or

part of a program in other applications.

Interoperability: effort required interconnecting or relating

two different applications, running possibly in different

computing environments.

Usability: effort required to learn, operate and use a program


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SQE Activities

QA Activities need additional support: Planning and goal setting

Management:

When to start and stop?

Adjustment and improvement, etc Assessment

Assessment of quality/reliability, etc:

Data collection

Analysis and modeling

Providing feedback for management

QA + above Software Quality Engineering (SQE)


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SQE Process

Different customers have different quality expectationsunder different market environments.

We need to manage these quality expectations as an engineering

problem by meeting these expectations through the selection and

execution of appropriate Quality Assurance (QA) activities while

meeting project constraints such as cost and project schedule,project risk, etc.

Quality management provides an independent check on the

software development process.


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SQE Process

Quality Engineering Process consist of: Pre-QA Activity

In-QA Activity / QA activity

Post-QA Activity / Analysis and Feedback


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SQE Process

Figure: Software quality engineering process


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SQE Process Pre-QA Activity

Pre-QA Activity Quality Planning

Quality planning should begin at an early stage in the

software process.

The result of the quality planning process is theproject quality plan.

These activities should carried out before the regular

QA activities.

Two major types of pre-QA activities Set specific quality goals

Form QA strategy

Select appropriate QA activities to perform

Choose appropriate quality measurements and models to

provide feedback, quality assessment and improvement


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SQE Process In-QA Activity

In-QA Activity / QA activity Executing planned QA activities

Handling discovered defects

These activities were discussed in last two lectures.


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SQE Process Post-QA Activity

Post-QA Activity Quality measurement, assessment and improvement

These activities are carried out after normal QA

activities have started but not as part of these normal

activities. The primary purpose of these activities is to provide

quality assessment and feedback so that various

management decisions can be made and possible

quality improvement initiatives can be carried out.

Post-QA does not men after the finish of QA activities,

it could be carried out parallel to QA activities


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Pre-QA Activity / Quality Planning

Goal Setting Forming QA strategy

Goal Setting:

Satisfy customers quality expectations economically

by the software development process. How? Identify quality view and attributes

Select direct quality measures ( to measure the selected

quality attributes from customers perspective)

Assess quality expectation vs. cost


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Identify quality view and attributesCustomers/user expectations

Market condition

Product type, etc

Select direct quality measuresReliability: primary concern - business/commercial software

Safety: Primary concern air traffic control system (real-time

control system), embedded software in automobile, medical

device, etc.

Usability: Primary concern - Personal utilities software,

instead of reliability or safety.

These quality views and attributes could be found in close

cooperation with the customers and user or these who

represents their interest, such as requirement analysts,

marketing personal, etc.


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Assess quality expectation vs. cost Cost-of-quality

Economic models: COCOMO (Constructive Cost Model)


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Forming QA strategy After fixing the quality goals, we can fix appropriate

QA activities

Evaluate individual QA alternatives

Strength/weakness/const/applicability, etc

Measurement and feedback planning

To achieve quality goals we need to know where we are and

how far away we are from the specific quality goals.


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In-QA Activity / QA activity

Discussed in last two lectures.


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Analysis and Feedback The primary purpose of this activity is to provide

quality assessment and feedback for the

management to make decisions, like- product release

can be made and possible quality and process

improvement initiatives can be carried out.

Measurement:

Defect measurement as part of defect handling process

These measurements data input to the subsequent analysis

and modeling activities that provide feedback and usefulinformation to manage software project and quality (historical

baseline).


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Analysis and modeling: Input: above data

Output/goal: feedback and follow-up (assessment of current

product quality, accurate predication of future quality)

Feedback and follow-up:

Results from the analysis and modeling activities can providefeedback to the quality engineering process to help us make

project scheduling, resource allocation, and other management

decisions.

Follow-up activities:

Results from these analysis and modeling activities could beapplied immediate or long term quality control strategies.

Example: If major changes are suggested for the quality

engineering process or software development process, they

typically need to wait unitil the current process is finished to

avoid unnecessary disturbance and risk to the current project.


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SQE in Software Development Process

QA activities carried out and integrated into the

software development process (covered last lecture)

Now we want to integrate Quality Engineering(pre-QA planning and post-QA measurement and

analysis activities) activities to software

development process


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SQE in Software Development Process Contd

SQE activities Development process

Quality Planning Product Planning

Example: In waterfall model, carried out in the phase for

market analysis, requirement analysis, and product

specification. Such information provide us with valuable information about

quality expectations by target customers and users in the

specific market.

Quality goals can be planned and set accordingly

QA activity development activities Analysis/feedback Project management


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SQE in Waterfall Model

Fig: SQE in Waterfall Model


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SQE in Waterfall Model

Quality Planning: Starts with requirement analysisphase

QA activities: Starts just after the quality planningphase

Measurement and analysis: starts after the QAactivities phase


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SQE Effort Profile

The overall quality engineering effort over time is divided

into three parts

Fig: SQE effort in waterfall process


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SQE Effort Profile

The bottom part represents the share of total effort by

quality planning activities

The middle part represents the share of total effort for

the execution of selected QA activities

The upper part represents the share of total effort for the

measurement and quality assessment activities

l 04 z quality engineering

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