-Suhas Nayak

What is it?

Formal design and requirements methods

+Statistical Usage Testing

______________________________Little or No Defects

Why Cleanroom?O QualityO Most suitable for critical applicationsO Increased ProductivityO Reduces Costs

Cleanroom Methodology

O Requirements AnalysisO High-level DesignO Detailed DesignO Coding by incrementO Pretest by incrementO Statistical Testing by increment

Incremental Development Cycle

O Early and continual quality assessment

O Increased user feedbackO Repair any process related problemsO Allow requirements changes

Formalspecification

Develop s/wincrement

Establishrerquirements

Deliversoftware

Frozenspecification

Requirements change request

Cleanroom Principles - part 1

O Small teamsO independent specification, development,

and certification sub-teamsO Incremental development under statistical

quality controlO performance assessed during each

increment using measure like number of sequential error-free test cases

O feedback is used for process improvement and the development plan is adjusted as needed

Cleanroom Process Teams

O Specification teamO develops and maintains the system

specificationO Development team

O develops and verifies softwareO the software is not compiled or executes during

verificationO Certification team

O develops set of statistical test to exercise software after development

O reliability growth models used to assess reliability

Cleanroom Principles - part 2

O Software development based on mathematical principlesO the box principle is used for specification and

designO formal verification is used to confirm correctness

of implementation of specificationO program correctness is verified by team reviews

using questionnairesO Testing based on statistical principles

O operational usage profiles neededO test cases are randomly generated from the usage

modelO failure data is interpreted using statistical models

Functional Specification

Modeling approach in cleanroom software engineering uses a method called box structure specification

OBlack BoxOState BoxOClear Box

Fig: Box Structure Refinement

BB1

BB 1.1

BB1.2

BB1.n

BB.1.1.1

BB1.1.2

BB1.1.3

SB1.1.1

CB1.1.1.1

CB1.1.1.2

CB1.1.1.3

Cleanroom Strategy - part 1

O Increment planning.O The project plan is built around the

incremental strategy.O Requirements gathering.

O Customer requirements are elicited and refined for each increment using traditional methods.

O Box structure specification. O Box structures isolate and separate the

definition of behavior, data, and procedures at each level of refinement.

Cleanroom Strategy - part 2

O Formal design.O Specifications (black-boxes) are

iteratively refined to become architectural designs (state-boxes) and component-level designs (clear boxes).

O Correctness verification. O Correctness questions are asked and

answered, formal mathematical verification is used as required.

Cleanroom Strategy - part 3

O Code generation, inspection, verification. O Box structures are translated into

program language; inspections are used to ensure conformance of code and boxes, as well as syntactic correctness of code; followed by correctness verification of the code.

O Statistical test planning. O A suite of test cases is created to match

the probability distribution of the projected product usage pattern.

Cleanroom Strategy - part 4

O Statistical use testing. O A statistical sample of all possible test

cases is used rather than exhaustive testing.

O Certification. O Once verification, inspection, and usage

testing are complete and all defects removed, the increment is certified as ready for integration.

Cleanroom Process Overview

Constructstructuredprogram

Definesoftware

increments

Formallyverifycode

Integrateincrement

Formallyspecifysystem

Developoperational

profileDesign

statisticaltests

Testintegrated

system

Error rework

ConclusionO Key Characteristics of Cleanroom SE

O Incremental Development Life CycleO Defect Prevention: Quality

Assessment thru Statistical TestingO Disciplined SE methods required to

create correct, verifiable software

ResourcesO Software Engineering – Roger S

PressmanO www.suhas-angelus/blogspot.com

Question Time!!