1 chapter 3 1.quality management, 2.software cost estimation 3.process improvement

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Chapter 3

1. Quality Management,

2. Software Cost Estimation

3. Process Improvement

Software Engineering Application Development----> Chapter 3

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Process and product qualityQuality assurance and standardsQuality control

Quality Management


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Software quality management

Concerned with ensuring that the required level of quality is

achieved in a software product.

Involves defining appropriate quality standards and

procedures and ensuring that these are followed.

Should aim to develop a ‘quality culture’ where quality is

seen as everyone’s responsibility.


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What is quality?

Quality, means that a product should meet its specification.

Some quality requirements are difficult to specify in an unambiguous way

Software specifications are usually incomplete and often unpredictable.


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Quality management activities Quality assurance

Establish organisational procedures and standards for quality.

Quality planning Select applicable procedures and standards for a particular project and

modify these as required.

Quality control Ensure that procedures and standards are followed by the software

development team.

Quality management should be separate from project management to ensure independence.


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• Standards are the key to effective quality management. They may

be international, national, organizational or project standards.

• Product standards define characteristics that all components

should exhibit. e.g. a common programming style.

• Process standards define how the software process should be

Performed.

Quality Assurance and Standards


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Product and Process Standards

Product standards Process standards

Design review form Design review conduct

Requirements document structure Submission of documents to CM

Method header format Version release process

Java programming style Project plan approval process

Project plan format Change control process

Change request form Test recording process


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Encapsulation of best practice- avoids repetition of past mistakes.

They are a framework for quality assurance processes - they

involve checking compliance to standards.

They provide continuity - new staff can understand the

organisation by understanding the standards that are used.

Importance of standards


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Software Quality Attributes

Safety Understandability Portability

Security Testability Usability

Reliability Adaptability Reusability

Resilience Modularity Efficiency

Robustness Complexity Learnability


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Quality control

• This involves checking the software

development process to ensure that procedures

and standards are being followed.

• There are two approaches to quality control– Quality reviews;– Automated software assessment and software

measurement.


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Quality reviews• This is the principal method of validating the quality of a process

or of a product.

• A group examines part or all of a process or system and its

documentation to find potential problems.

• There are different types of review with different objectives

– Inspections for defect removal

– Reviews for progress assessment

– Quality reviews (product and standards).


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Software Measurement and Metrics• Software measurement is concerned with deriving a numeric

value for an attribute of a software product or process.

• Measure - quantitative indication of amount, dimension, capacity, or size of some attribute of a product or process.

• Metric - quantitative measure of degree to which a system, component or process holds a given attribute. “A handle or guess about a given attribute.”

Software Measurement and Metrics

• Why Measure Software?– To determine the quality of the current product or process– To predict qualities of a product/process– To improve quality of a product/process


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• Budget - To know what you will spend

• Controls - A lever to control the project

• Differential analysis - Monitor progress by comparing planned with estimated costs

• Cost database - Make future estimation better

• Marry costing to management - Cost estimation and planning/scheduling are closely

related activities

Software Cost Estimation


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Estimation Techniques

1. Expert judgment

2. Estimation by analogy

3. Pricing to win

4. Top-down estimation

5. Bottom-up estimation

6. Algorithmic cost modeling


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• One or more experts in both software development and the

application domain use their experience to predict software costs.

Process iterates until an agreement is reached.

• Advantages: Relatively cheap estimation method. Can be accurate

if experts have direct experience of similar systems

• Disadvantages: May be very costly

(1) - Expert judgement


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• The cost of a project is computed by comparing the project to a

similar project in the same application domain.

• Advantages: Accurate if project data available

• Disadvantages: Impossible if no comparable project has been

tackled. Needs systematically maintained cost database.

Estimation by analogy


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• The project costs whatever the customer has to spend on it.

• Advantages: You get the contract.

• Disadvantages: The probability that the customer gets the

system he/she wants is small. Costs do not accurately reflect

the work required

Pricing to win


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• Start at system level and work out how the system functionality is

provided.

• Usable without knowledge of the system architecture and the components that might be part of the system.

• Takes into account costs such as integration, configuration management

and documentation

• Can underestimate the cost of solving difficult low-level technical

problems.

Top-down estimation


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• Start at the lowest system level. The cost of each component is

estimated individually. These costs are added to give final cost

estimate.

• Accurate method if the system has been designed in detail.

• May underestimate costs of system level activities such as

integration and documentation.

Bottom-up estimation


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– Each method has strengths and weaknesses. Therefore,

estimation should be based on several methods

– If these do not return approximately the same result, there is

insufficient information available

–Pricing to win is sometimes the only applicable method

Estimation methods


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• Cost is estimated as a mathematical function of product, project

and process attributes whose values are estimated by project

managers.

• Most commonly used product attribute for cost estimation

• Most models are basically similar but with different attribute

values

Algorithmic cost modelling


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Process Improvement

Understanding, Modelling and Improving the Software Process

• Process and product quality• Process analysis and modelling• Process measurement• Process classification


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The Process Improvement Cycle

Analyse

Measure

Change


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• Understanding existing processes

• Introducing process changes to achieve organisational

objectives which are usually focused on quality improvement,

cost reduction and schedule acceleration

• Most process improvement work so far has focused on defect

reduction. This reflects the increasing attention paid by industry

to quality

• However, other process attributes can be the focus of

improvement

Process Improvement


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Process attributes


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• Process analysis– Model and analyse (quantitatively if possible) existing processes

• Improvement identification– Identify quality, cost or schedule bottlenecks

• Process change introduction– Modify the process to remove identified bottlenecks

• Process change training– Train staff involved in new process proposals

• Change tuning– Evolve and improve process improvements

Process improvement stages


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• Process quality and product quality are closely related

• A good process is usually required to produce a good product

• For manufactured goods, process is the principal quality

determinant

Process and product quality


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Process Improvement



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Process analysis and modelling• Process analysis

– The study of existing processes to understand the relationships

between parts of the process and to compare them with other

processes

• Process modelling

– The documentation of a process which records the tasks, the

roles and the entities used

– Process models may be presented from different perspectives

(examples ?)


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• Questionnaires and interviews

– Must be carefully designed. Participants may tell you what

they think you want to hear

• Ethnographic analysis

– Involves assimilating process knowledge by observation

Process analysis techniques


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Process Improvement



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• Wherever possible, quantitative process data should be collected

– However, where organisations do not have clearly defined process

standards this is very difficult as you don’t know what to measure. A

process may have to be defined before any measurement is possible

• Process measurements should be used to assess process improvements

– But this does not mean that measurements should drive the

improvements. The improvement driver should be the organizational

objectives

Process measurement


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Process Improvement



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• Informal– No detailed process model. Development team chose

their own way of working. Works with prototypes & short lifetime products

• Managed– Defined process model which drives the development

process. Works with large systems & long lifetime products

• Methodical– Defined development methods supported by CASE tools

• Improving– improvements considered and introduction procedures

Process classification


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• Process used should depend on type of product which is being developed– For large systems, management is usually the principal

problem so you need a strictly managed process. For smaller systems, more informality is possible.

• There is no uniformly applicable process which should be standardised within an organisation– High costs may be incurred if you force an inappropriate

process on a development team

Process choice


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Thank you

1 chapter 3 1.quality management, 2.software cost estimation 3.process improvement

Documents

quality reviewsthis

quality culture

quality controlensure

appropriate quality

quality requirements

software product

software development

software process