Se lect12 btech

Deliverables by Phase

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Deliverables by Phase

SoftwareConcept

Requirements

Analysis

Design

Coding andDebugging

SystemsTesting

Deployment &Maintenance

Possible Deliverables by Phase Concept Document Statement of Work (SOW) Project Charter RFP & Proposal

Requirements Document (Software Requirements Specification) Work Breakdown Structure (WBS)

Functional Specification ( Top Level Design Specification) Entity Relationship Diagram Data Flow Diagram

Detailed Design Specification Object Diagrams Detailed Data Model

Coding Standards Working Code Unit Tests

Acceptance Test Procedures Tested Application

Maintenance Specification Deployed Application

Project Development Plan (Software Development Plan ) Baseline Project Plan Quality Assurance Plan Configuration Management Plan Risk Management Plan

Integration Plan Detailed SQA Test Plan SQA Test Cases

User Documentation Training Plan

Risk management

Risk management is concerned with identifying risks and drawing up plans to minimise their effect on a project.

A risk is a probability that some adverse circumstance will occur. Project risks affect schedule or resources Product risks affect the quality or performance of the

software being developed Business risks affect the organisation developing or

procuring the software

Software risksRisk Risk type DescriptionStaff turnover Project Experienced staff will leave the

project before it is finished.Management change Project There will be a change of

organisational management withdifferent priorities.

Hardware unavailability Project Hardware which is essential for theproject will not be delivered onschedule.

Requirements change Project andproduct

There will be a larger number ofchanges to the requirements thananticipated.

Specification delays Project andproduct

Specifications of essential interfacesare not available on schedule

Size underestimate Project andproduct

The size of the system has beenunderestimated.

CASE tool under-performance

Product CASE tools which support theproject do not perform as anticipated

Technology change Business The underlying technology on whichthe system is built is superseded bynew technology.

Product competition Business A competitive product is marketedbefore the system is completed.

The Risk Management Process

• Risk identification– Identify project, product and business risks

• Risk analysis– Assess the likelihood and consequences of these

risks

• Risk planning– Draw up plans to avoid or minimise the effects of the

risk

• Risk monitoring– Monitor the risks throughout the project

The risk management process

Risk avoidanceand contingency

plans

Risk planning

Prioritised risklist

Risk analysis

List of potentialrisks

Riskidentification

Riskassessment

Riskmonitoring

Risk identification

• Technology risks

• People risks

• Organisational risks

• Requirements risks

• Estimation risks

Risks and risk types

Risk type Possible risksTechnology The database used in the system cannot process as many

transactions per second as expected.Software components which should be reused contain defectswhich limit their functionality.

People It is impossible to recruit staff with the skills required.Key staff are ill and unavailable at critical times.Required training for staff is not available.

Organisational The organisation is restructured so that different managementare responsible for the project.Organisational financial problems force reductions in the projectbudget.

Tools The code generated by CASE tools is inefficient.CASE tools cannot be integrated.

Requirements Changes to requirements which require major design rework areproposed.Customers fail to understand the impact of requirementschanges.

Estimation The time required to develop the software is underestimated.The rate of defect repair is underestimated.The size of the software is underestimated.

Risk analysis

• Assess probability and seriousness of each risk• Probability may be

– very low– low– moderate – high or very high

• Risk effects might be – catastrophic – serious– Tolerable – insignificant

Risk analysis

Risk Probability EffectsOrganisational financial problems force reductionsin the project budget.

Low Catastrophic

It is impossible to recruit staff with the skillsrequired for the project.

High Catastrophic

Key staff are ill at critical times in the project. Moderate SeriousSoftware components which should be reusedcontain defects which limit their functionality.

Moderate Serious

Changes to requirements which require majordesign rework are proposed.

Moderate Serious

The organisation is restructured so that differentmanagement are responsible for the project.

High Serious

The database used in the system cannot process asmany transactions per second as expected.

Moderate Serious

The time required to develop the software isunderestimated.

High Serious

CASE tools cannot be integrated. High TolerableCustomers fail to understand the impact ofrequirements changes.

Moderate Tolerable

Required training for staff is not available. Moderate TolerableThe rate of defect repair is underestimated. Moderate TolerableThe size of the software is underestimated. High TolerableThe code generated by CASE tools is inefficient. Moderate Insignificant

Risk planning

Consider each risk and develop a strategy to manage that risk

Avoidance strategies The probability that the risk will arise is reduced

Minimisation strategies The impact of the risk on the project or product will

be reducedContingency plans

If the risk arises, contingency plans are plans to deal with that risk

Risk management strategies

Risk StrategyOrganisationalfinancial problems

Prepare a briefing document for senior management showinghow the project is making a very important contribution to thegoals of the business.

Recruitmentproblems

Alert customer of potential difficulties and the possibility ofdelays, investigate buying-in components.

Staff illness Reorganise team so that there is more overlap of work andpeople therefore understand each other’s jobs.

Defectivecomponents

Replace potentially defective components with bought-incomponents of known reliability.

Requirementschanges

Derive traceability information to assess requirements changeimpact, maximise information hiding in the design.

Organisationalrestructuring

Prepare a briefing document for senior management showinghow the project is making a very important contribution to thegoals of the business.

Databaseperformance

Investigate the possibility of buying a higher-performancedatabase.

Underestimateddevelopment time

Investigate buying in components, investigate use of a programgenerator.

Risk monitoring

• Assess each identified risks regularly to decide whether or not it is becoming less or more probable

• Also assess whether the effects of the risk have changed

• Each key risk should be discussed at management progress meetings

Risk factors

Risk type Potential indicatorsTechnology Late delivery of hardware or support software, many

reported technology problemsPeople Poor staff morale, poor relationships amongst team

member, job availabilityOrganisational organisational gossip, lack of action by senior

managementTools reluctance by team members to use tools, complaints

about CASE tools, demands for higher-poweredworkstations

Requirements many requirements change requests, customercomplaints

Estimation failure to meet agreed schedule, failure to clearreported defects

Software Measurement & Matrices

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Software Measurement Objectives

– Assessing status• Projects• Products for a specific project or projects• Processes• Resources

– Identifying trends• Need to be able to differentiate between a healthy project and one

that’s in trouble

– Determine corrective action• Measurements should indicate the appropriate corrective action, if

any is required.

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Software Measurement Objectives

• Types of information required to understand, control, and improve projects:– Managers

• What does the process cost?• How productive is the staff?• How good is the code?• Will the customer/user be satisfied?• How can we improve?

– Engineers• Are the requirements testable?• Have all the faults been found?• Have the product or process goals been met?• What will happen in the future?

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The Scope of Software Metrics

– Cost and effort estimation– Productivity measures and models– Data collection– Quality models and measures– Reliability models– Performance evaluation and models– Structural and complexity metrics– Capability-maturity assessment– Management by metrics– Evaluation of methods and tools

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The Scope of Software Metrics

• The Scope of Software Metrics – some details– Possible productivity model

Productivity

ValueCost

QuantityQuality

Reliability Defects FunctionalitySize

Personnel Resources Complexity

Time

Money

HW

SW

Env Cnstrst

Problem difficulty

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The Scope of Software Metrics• The Scope of Software Metrics – some

details– Software quality model

Use Factor Criteria

Product Operation

Product Revision

Usability

Reliability

Efficiency

Reusability

Maintainability

Portability

Testability

Communicativeness

Accuracy

Consistency

Device Efficiency

Completeness

Structuredness

Conciseness

Device Independence

Legibility

Self-descriptiveness

Traceability

Accessibility

Metrics

Direct and Indirect Matrices

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Measurement Basics

• Direct and Indirect Measurement– Direct measure – relates an attribute to a number or

symbol without reference to no other object or attribute (e.g., height).

– Indirect measure• Used when an attribute must be measured by combining

several of its aspects (e.g., density)

• Requires a model of how measures are related to each other

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Measurement Basics

• Direct and Indirect Measures for Software – examples– Direct

• Length or source code (lines of code)• Duration of testing process• Number of defects discovered during test• Time a developer spends on a project

– Indirect• Programmer productivity (LOC/workmonths of effort)• Module defect density (number of defects/module size)• Defect detection efficiency (# defects detected/total defects)• Requirements stability (initial # requirements/total # requirements)• Test effectiveness ratio (number of items covered/total number of items)• System spoilage (effort spent fixing faults/total project effort)

Quality Models and Measures

Software product quality metrics

• The quality of a product:

- the “totality of characteristics that bear on its ability to satisfy stated or implied needs”.

Metrics of the external quality attributes producer’s perspective: “conformance to

requirements” customer’s perspective: “fitness for use”

- customer’s expectations

Quality metrics

• Two levels of software product quality metrics:

Intrinsic product quality

Customer oriented metrics

Intrinsic product quality metrics:

Reliability: number of hours the software can run

before a failure

Defect density (rate):

number of defects contained in software, relative

to its size.

Customer oriented metrics:

Customer problems

Customer satisfaction

Intrinsic product quality metrics

Reliability --- Defect density

• Correlated but different!

• Both are predicted values.

• Estimated using static and dynamic models

Defect: an anomaly in the product (“bug”)

Software failure: an execution whose effect is not conform to software specification

Reliability

Reliability metrics:

MTBF (Mean Time Between Failures)

MTTF (Man Time To Failure)

MTBF (Mean Time Between Failures):

the expected time between two successive failures of a system

expressed in hours

a key reliability metric for systems that can be repaired or restored

(repairable systems)

applicable when several system failures are expected.

For a hardware product, MTBF decreases with the its age.

MTTF (Man Time To Failure):

the expected time to failure of a system

in reliability engineering metric for non-repairable systems

non-repairable systems can fail only once; example, a satellite is not repairable.

Mean Time To Repair (MTTR): average time to restore a system after a failure

When there are no delays in repair: MTBF = MTTF + MTTR

Software products are repairable systems!

Reliability models neglect the time needed to restore the system after a failure.

with MTTR =0 MTBF = MTTF

Availability = MTTF / MTBF = MTTF / (MTTF + MTTR)

3.1.2. Defect rate (density)

Number of defects per KLOC or per Number of Function Point,

in a given time unit

Example:

“The latent defect rate for this product, during next four years, is 2.0

defects per KLOC”.

Crude metric: a defect may involve one or more lines of code

Lines Of Code

-Different counting tools

-Defect rate metric has to be completed with the counting method for LOC!

-Not recommended to compare defect rates of two products written in

different languages

Reliability or Defect Rate ?

Reliability:

often used with safety-critical systems such as: airline traffic control systems,

avionics, weapons.

(usage profile and scenarios are better defined)

Defect density:

in many commercial systems (systems for commercial use)

• there is no typical user profile

• development organizations use defect rate for maintenance cost and

resource estimates

• MTTF is more difficult to implement and may not be representative of all

customers.

Customer Oriented Metrics

Customer Problems MetricCustomer Problems Metric

Customer problems when using the product:

valid defects, usability problems, unclear documentation, user errors.

Problems per user month (PUM) metric:

PUM = TNP/ TNM

TNP: Total number of problems reported by customers for a time period

TNM: Total number of license-months of the software during the period

= number of install licenses of the software x number of months in the period

3.2.2. Customer satisfaction metrics

Often measured on the five-point scale:1. Very satisfied2. Satisfied3. Neutral4. Dissatisfied5. Very dissatisfied IBM: CUPRIMDSO (capability/functionality, usability, performance, reliability,

installability, maintainability, documentation /information, service and overall)

Hewlett-Packard: FURPS (functionality, usability, reliability, performance and service)

Ishikawa’s Seven Basic Tools for Quality Control

• Checklist (or Check Sheet) – to facilitate gathering data and to arrange data so it can be easily used later

• Pareto Diagram – a frequency chart of bars in descending order; the bars are usually associated with types of problems

• Histogram – a graphic representation of frequency counts of a sample or a population

• Scatter Diagram – portrays the relationship of two interval variables; can make outliers clear

• Run Chart – tracks the performance of the parameter of interest over time; used for trend analysis

• Control Chart – an advance form of a run chart for situations in which the process capability can be defined

• Cause and Effect Diagram (fishbone diagram) – it shows the relationship between a characteristic and the factors that affect that relationship

Ishikawa’s Seven Basic Tools for Quality Control

Checklists

• Summarize the key points of the software development process

• More effective than lengthy process documents• Help ensure that all tasks are complete and the

important factors or quality characteristics of each task are covered

• Examples of checklists are:– Design review checklist– Code inspection checklist– Moderator (for review and inspection) checklist– Pre-code-integration checklist– Entrance and exit criteria for system tests– Product readiness checklist

Pareto Diagram

• Identifies areas that cause most of the problems

Pareto Analysis of Software Defects

Pareto Diagram of Defect by Component Problem Index

Histograms

Profile of Customer Satisfaction with a Software Product

Scatter Diagram of Program Complexity and Defect Level

Correlation of Defect Rates of Reused Components Between Two Platforms

Grouping of Reused Components Based on Defect Rate Relationship

Pseudo-Control Chart of Test Defect Rate—First Iteration

Pseudo-Control Chart of Test Defect Rate—Second Iteration

Pseudo-Control Chart of Inspection Effectiveness

Cause-and-Effect Diagram

Cause-and-Effect Diagram of Design Inspection

A Schematic Representation of a Relations Diagram