Quality assurance ch#1

Quality - Conformance to requirement (Crosby, 1979):

1. The requirements are clearly stated and the product must conform to it. 2. Any deviation from the requirements is regarded as a defect. 3. A good quality product contains fewer defects.

Detection

Defects/errors are noticed (identified) afterwards and are then corrected.

Software Quality Perspectives (Maintenance engineer)

Detection and correction times.

Deliberate deviations from software requirements.

Developer reuses already built software modules, omitting required functions due to time/budget constraints, ...

Procedure errors

e.g. procedures that direct the user with respect to the activities required at each step of the process.

Non-compliance with documentation and coding instructions.

e.g., difficulties in understanding "non-complying" code, difficulties in reviewing non-complying team design...

Faulty requirements definition.

e.g., erroneous definition of requirements, absence of vital requirements, ...

Logical design errors.

e.g., erroneous of boundary conditions, ...

Shortcomings of the Testing Process

e.g., incomplete test plan, failure to report errors and faults, ...

Client-developer communication failures.

e.g., misunderstanding of client's instructions, misunderstanding of client's written changes requirement...

Documentation errors

e.g., omission of software functions, listing non-existing functions, ...

characteristics of software engineering

especially its systematic, disciplined approach, make SW engineering a good environment for achieving SQA objectives.

Quality Control (QC)

is a set of activities carried out with the main objective of withholding products from shipment if they do not qualify.

Quality Assurance (QA)

minimize the costs of quality by introducing activities throughout the development process in order to prevent the causes of errors, detect them, and correct them in the early stages. As a result, it reduces the rates of non-qualifying products.

Software engineering is

the application of a systematic, disciplined, quantifiable approach to the development, operation and maintenance of software.

Software Quality should be Considered in:

• Infrastructure and tools. • Staff. • Contract. • SDLC ( Requirements, design, implementation, ...). • Budget. • Schedule. • Maintenance.

SQA - Expanded Definition Software quality assurance is:

A systematic, planned set of actions necessary to provide adequate confidence that the software development process or the maintenance process of a software system product conforms to established functional technical requirements as well as with the managerial requirements of keeping the schedule and operating within the budgetary confines.

Software Fault

All SW errors may not cause software faults. Because, that part of the SW may not be executed.

4 components of software

■ Computer programs (the "code"). ■ Procedures. ■ Documentation. ■ Data necessary for operating the software system.

Software Quality Perspectives (Customer)

Complete requirements (Functional and non-functional).

Software

Computer programs, procedures, and possibly associated documentation and data pertaining to the operation of a computer system.

Software Quality Perspectives (Project manager)

Cost and schedule.

Software Quality- IEEE Definition

1. The degree to which a system, component, or process meets specified requirements. 2. The degree to which a system, component, or process meets customer or user needs or expectations.

Software quality assurance is:

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.

The Objectives of SQA Activities in Software Development Software development (process-oriented):

1. Assuring, with acceptable levels of confidence, conformance to functional requirements. 2. Assuring, with acceptable levels of confidence, conformance to managerial requirements of scheduling and budgets.

Benefits of Software Quality

1. Decreased number of defects and errors in software. 2. Less rework as a result of less software defects. 3. Reduced development and maintenance cost. 4. Increased software reliability. 5. Increased customer satisfaction. 6. Happier software practitioners.

Classification of the 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 errors.

Quality - Fitness for use (Juran, 1970):

1. Fit to user expectations: meet users needs and satisfaction. 2. A good quality product provides better user satisfaction.

Software engineers strive to control the

1. Process applied: What is the best process (i.e SDLC) to be used for the development of software. 2. Resources expended: Make sure software development is finished in expected time and also using the estimated budget. 3. End product quality attributes: Make sure that the software itself is of a high quality and contains all features and requirements (functional and non-functional).

Three level of organizations are aimed at maintaining the production of quality:

1. Quality Management (QM). 2. Quality Assurance (QA). 3. Quality Control (QC).

Four absolutes of quality

1. Quality Means Conformance to Requirements. (Both functional and Non- functional) 2. Quality is never ending improvement. 3. Quality is Zero Defects. 4. Quality comes from Prevention, not detection.

Software Failures

A SW fault becomes a SW failure when/if it is activated. - Faults may be found in the software due to the way the software is executed. - Other constraints on the software's execution, such as execution options.

Prevention

Keeping defects from happening in the first place, through checks and other restrictions [Do it right from the first time].

Software Error

Made by the programmer - Syntax (grammatical) error. Ex. Opening a bracket without closing it. - Logic error (multiply instead of adding two operands).