Product Quality and Process
Quality.CHAPTER-4
Product-Software Applications(final outcome of SDLC)
Process-Steps followed to create s/w. eg: Analysis, Design… SDLC stages.
Quality is common in attribute and it is different for process and product.
Product Qualiy:
1)Business Req Complex,
So process->complex,literate ,customer demands and more.
1)s/w is not a mass production.eg:cellphone.groupof members develop one
software.
2)s/w will degrade over time(will not wear out).
Windows98-> not in use
Enhanced version is used now
3) s/w is assembled from existing component( component reuse)
h/w characteristics:
1)mass production (in lakhs)
2)h/w will wear out
3)assembling will be done by fresh component but reusability is rare.
3) PRODUCT QUALITY
-good infrastructure is required to create quality.ex:rational rose for UML
diagram winrunner for s/w testing(process)
-framework/ infrastructure is mainly for process( blackboard->
infrastructure, writing->process)
->s/w attribute and characteristics and meeting requirements -> quality
measurement parameters
->attributes are defined in 2 levels
-development
-delivery
1)s/w attributes
-standards and practices must be define d early
1)reliability: s/w should not fail
2)usability: easy to use
3)functionality: words spell check
4)maintenance: to what extent sw can be modified in future
Classification of s/w application attributes
1)performance attribute: execution characteristics how it works in real environment
2)form attribute: appearance( look and feel) how it appears
3)processing attribute: processing characteristic . how system s/w carries out it
intended actions
4)function attribute: describes the functionality of the s/w that is the action
performed
5)operational integrity:
-describes reliability, system control and operational support
-degree of user requirement support
6)maintainability: the ability to accommodate changing requirements in a simple
manner
4.4 MODELS FOR S/W PRODUCT QUALITY
1.Mc calls factor- Criteria Metric Model
-this model was originally developed for the US airforce and for evaluating s/w
product quality
Basic Theme:
Any s/w product will have high level quality factors and these factors can be
defined in terms of criteria
Each criteria is measured with metrices(rating or measurement)
Purpose of model:
To define the characteristics of s/w products to be assessed
To suggest methods to capture the characteristics
Ex: high level , usability, modularity
-main focus of the model is on the final product
-this model will identify for quality attributes( key factors) from user point of view
-quality criteria is obtained by decomposing high level quality factors into low
level attributes
-reliability, accuracy, completeness, consistency( uniformity) [refer table pg
85,86]
2)The ISO 9126 standard quality model
-multiple models for quality existed
-users wanted a single model/ universal (assessment people) model which makes
comparison easier
-Mc call’s model is used as a base to derive a new model basis for international
standard for quality assessment
-this name of model is ‘s/w product evaluation: quality characteristics and
guidelines for their use’
-code-> ISO 9126
-definition for s/w quality: “pg 87”
Quality Factors:
-functionality
-reliability
-attributes are comprehensive
-each factor can be broken into multiple levels
Other models:
Goal – metric model – developed by basiliand rombach basic idea:- metric are
derived from measurement goals and questions –related to quality characteristics .
Define –your – own – model approach–
-developed by gilb and kitchenham
-based on evolutionary software development (evolutionary models are iterative .
iteration – completion module by module
- similar to MC calls model – high level factors decomposed into measurable
attributes
-as per gilbs approach, a product will be delivered in increments ( ie module wise ).
-prioritization of modules becomes essential to determining incremental sequence.
- a large project may have number of moduels. Modules should
-priority is decided given by priority using the key software attributes.
- eg page 90.
- COQUAMO(constructive quality model)
-developed by kitchenham and walker.
-based on gilbs model .
-supported by automated tool(ie quality is evaluated using automated tools)
-E SPRIT project
- at times , quality attributes conflict each other.
Requirement collector must be aware of attribute conflicts .
-[efficiency and low cost – both attributes conflict each other]
-quality metric definition by IEEE standard :- a quantitative
5. process quality
Software quality is defined as “totality (sum ) of features and characteristics of a
product or servers whose abilty process – steps used to create a product ”.
-process quality – quality of those steps used to create a product
Two models exist to evaluate quality of a process
1.US standard -> ISO 9001
2.UK standard -> process maturity model.
3. Eropian standard -> capability maturity model.
Process has well defined beginning and end.
1 ISO 9000 series – Quality Mangement Standard(9000 to 9004) .
- ISO 9001 refers to a process approach for managing an organization. This
approach is PDCA cycle(Plan Do Check Act) refer page 91
- Sub section are available for management , quality system , internal audit
and corrective actions
- ISO standards will demand the following plans [ISO standard check various
documents of product]
• Development plan
• Quality plan
• Test plan
• Maintenance plan
- Each plan has a proper format or structure (activities ).
- A set of standards that support ISO 9003
- Each one is a process
• Configuration management
• Documentation control
• Quality record maintanence
• Process and product measurement
• Adoption of rules, practices and conventions
• Use of tools and techniques[eg : CASE tools , debugging tools, testing
tools]
• Purchasing hardware or software
• procedure for included software
• Training
- Role of ISO 9001 in the evaluation of a software product :-
• Designed for two parties
• Purchaser
• Supplier
• Also used for independent assessment
- Main objective
• Improve process quality
• It will not develop good quality process just for checking process
quality . process certificate are awarded for product that are
evaluated .
- 2. Matutity model for process quality :-
- Level 1 – Initial
- Level 2 – repeatable
- Level3 – defined
- Level 4- managed
- Level5 – optimal
These are five levels of capability maturity model -> used by organization to
evaluate process quality .
Capability maturity model is based on key process areas – commitment to
perform, ability to perform (pg :94)
-basic assumption of process quality models is that if the quality of the s/w
development process is good then product quality will be good.
-capability maturity model is only for s/w [but ISO 9000-9003 for s/w]
-in general ISO standards are used for s/w company , manufacturing company ,
institutions, govt sector
