CHAPTER 9

INSPECTIONS AS AN UP-FRONT QUALITY

TECHNIQUE

EARLY SKEPTIC

BELIEVER

FIRST HAND EXPERIENCE WITH PROPER INSPECTIONS

AND ITS REWARDS

AGENDA:

1 Anatomy of Inspection. Inspection Team Inspection Phases Inspection Types Wrap-up

2 Lessons learned through the evolution of the Inspection process.

3 Inspection Metrics 4 The National perspective 5 Examples of Payoff

Anatomy Of Inspection

Primary Purpose “..to remove defects as early as possible in the

development process.”

Secondary Purposes Trace requirements to design. Provide a technically correct base for next phase of

development. Increase programming quality Increase product quality Decrease life cycle cost Increase effectiveness of test activity Provide first indication of maintainability Encourage entry/exit criteria software management

Anatomy Of Inspection…

Inspection Team

MODERATOR

INSPECTORSREADER

AUTHOR

MANAGER

Inspection Phases

Planning: Starting PhaseThe moderator will Establish conduct & progress for entire process. Identify team members and roles Assure that materials to be inspected are

available and conform to standards. Determine entry criteria is met. Determine need for overview. Schedule meeting time and place. Provide team with materials, resources and

meeting notice.

Inspection Phases…

Overview: Discretionary PhaseThe Author: Gives a brief description of the product, its

functionality and interfaces.

The Attendees: Get familiar with product before the inspection

The Moderator: Conducts the overview meeting. Provides the inspection package to the team. Gives inspection meeting notice.

Inspection Phases…

Preparation: Begins at least 5 days before inspection meeting. Lead time to allow inspectors to examine the

material for all possible defects. Time spent – as much as duration of inspection

meeting – maximum of 2 hours. Inspectors record the defects and the time spent

in preparation. Reader prepares to present the material to the

team. Reader records any difficulties in understanding

the material.

Inspection Phases…

Inspection Meeting: The main event Team meets to inspect the product. Moderator ensures proper conduct of the meeting. Reader presents the product to the team in a

systematic manner. Team identifies, discusses, validates and records

the defects detected. Moderator decides if re-inspection is required. Moderator logs records of preparation and

inspection times, defects found and re-inspection requirement.

Moderator sends the findings to author and SQA.

Inspection Phases…

Rework: Author examines the defects and makes the

necessary fixes. Author verifies the fixes and informs moderator. Moderator determines if re-inspection required.

Follow-Up: Moderator assures that all defects logged have

been fixed. Moderator logs the verification and sends the

summary to SQE. Moderator declares inspection complete.

INSPECTION TYPES

REQUIREMENTS

PROGRAM SPECIFICATIONS

LOW-LEVEL OR DETAILED DESIGN

HIGH-LEVEL DESIGN

CODE IMPLEMENTATION

I0

I2

I1

SOFTWARE DEVELOPMENT PHASES

Inspection Types…

High-Level Design Inspection I0: Examine the HLD to verify that the

specification has been correctly mapped to functional design.

Identify each requirement to process and task.

One I0 per mode.

Perform all six inspection phases.

Inspection Types…

Low-Level Design Inspection I1: Held for any module that is new, has

structural or interface change, or 40% or more change in SLOC.

Verifies the detailed design before translation to code.

Perform all six inspection phases. Coding begins only after the successful

completion of this inspection.

Inspection Types…

Code Inspection I2: Held for all/selected new or changed

code. Code must compile cleanly. Perform all six inspection phases. Result of a successful I2 – Compiled code

that conforms to requirements specifications, high-level and low-level design.

Testing begins only after the successful completion of this inspection.

Inspection Types…Some more

Requirements Inspections Specification Inspections Document Inspections Salient Points:

Inspection is effective only when the product is presented in a standardized, structured form.

The results of these inspections, logged in a standardized form, can help the management in decision making.

Anatomy of Inspection – Wrap-up

Inspection Defect Types Design Defects Logic Defects Syntax Defects Standards Defects Data Defects Interface Defects Return code/Message Defects Prologue/Comment Defects Requirements change Defects Performance Improvement Defects

Inspections - Success Factors

Inspection Prerequisites Technically competent and trained inspectors. Trained moderator. Proper planning and distribution of materials. Good professional attitude. Full preparation prior to inspection meeting. Completed design or cleanly compiled code. Updated resource requirements. Training for managers to understand and gain

from inspections.

AGENDA:

1 Anatomy of Inspection. Inspection Team Inspection Phases Inspection Types Wrap-up

2 Lessons learned through the evolution of the Inspection process. 3 Inspection Metrics 4 The National perspective 5 Examples of Payoff

Lessons Learned

Keep the psychological factor in mind. – Help, don’t embarass!!!

Make inspections impersonal Keep team size to small groups of

peers Make data collection consistent Utilize only trained personnel.

Inspection Metrics

Established by AT&T Bell Labs. Defines nine metrics. Help plan, monitor, control and

improve code inspection process. Helped to achieve >70% defect

removal. Used the Goal-Question-Metric

paradigm to derive the nine metrics.

Inspection Metrics…

GQM paradigm Identify measurement goal. Pose specific question – in measurable terms –

whose answer fulfills the goal. Enumerate the metrics.

ExampleGoal – Monitor and ControlQuestion – What is the quality of the

inspected software?Metric – Average faults detected per KLOC

- Average inspection rate - Average Preparation rate

Inspection Metrics…

Total KLOC

Average lines of code inspected =

1000 x KLOC / #Inspections

Average Preparation rate =

1000 x KLOC / AvgInspectPrepTime

Average Inspection rate =

1000 x KLOC / TotInspectMeetingTime

Average Effort per KLOC =

TotInspectionEffort / KLOC

Inspection Metrics… (cont’d)

Average Effort per fault detected = TotalInspectEffort / #Faults_Detected

Average Faults detected per KLOC = #Faults_detected / KLOC

Percentage of re-inspections = 100 * #Re-Inspections / #Inspections

Defect removal efficiency = 100 x #Faults_Detected / #CodingFaults

AGENDA:

1 Anatomy of Inspection. Inspection Team Inspection Phases Inspection Types Wrap-up

2 Lessons learned through the evolution of the Inspection process. 3 Inspection Metrics 4 The National perspective 5 Examples of Payoff

National Software Quality Experiment

Reasons for the experiment Quality has become a national goal. Software Engineering is maturing. Aware consumers demand higher quality. Aggressive quality goals at corporate level.

Experiment - 1992 27 inspections labs 327 trained professionals 90,925 SLOC inspected using packaged

procedures. 22, 828 minutes of preparation effort 5,464 minutes of inspection time 1,849 defects detected

Examples of Payoff

AT&T Bell Laboratories Adopted Nine Metrics based on GQM paradigm Reduced cost of fault removal by 300% Defect Removal Efficiency of +70%

Bell Northern Research Inspections give 1 defect per person-hour

invested – 2-4 times faster than testing 1 person-hour of code inspection saves 33

person-hours of future maintenance effort.

Examples of Payoff…

Large Satellite Comm System The project was done in 1993. 330 KLOC on five target platforms with

many COTS products. 73 inspection meetings over 4 months #Defects recorded – 2,760 Cost Savings - $1 million

Cost to find and fix during test – Cost to find and fix via inspections prior to test

Examples of Payoff…

Raytheon Inspection = Defect Detection Process

DDP + Defect Prevention Process DPP Used DDP + DPP (1988-1994) Rework cost decrease: 45% to 5-10%. Increase software productivity 2.7x Reduced negative deviation from

budget and deadlines from 40% to near 0.

Reduced error density by factor of 3.

Final Words …

And

Questions???