cleanroom method

Cleanroom Method

CS 415, Software Engineering II

Mark Ardis, Rose-Hulman Institute

March 20, 2003

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Outline

1. Harlan Mills2. Cleanroom method3. Industrial use of cleanroom

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Harlan Mills

1919 - 1996

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Mathematics and Programming

Roman accounting"to go from programming as an instinctive, intuitive process to a more systematic, constructive process"

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Cleanroom Method

Incremental (spiral)

Box structure specification and design

Design verification

No debugging

Statistical testing

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Box Structures

Black boxes: behavior only

State Boxes: behavior + state

Clear boxes: procedures

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Black Boxes

S1S2...Sn R

stimulus history response

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State Boxes

S R

stimulus, old state response, new state

State Data

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Clear Boxes

S R

stimulus, old state response, new state

State Data

Procedures

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Box Description Language (BDL)

Invocation: use <type> <name> <args>

Sequence: do B1; B2 od

Alternation: if <cond> then B1 else B2 fi

Iteration: while <cond> do B od

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Box Structure Hierarchy

BB

SB

CB

BB BB BB

SB SB SB

CB CB CB

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Cartoon of the Day (1/3)

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Cartoon of the Day (2/3)

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Cartoon of the Day (3/3)

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Design Verification

Procedures in BDL are checked for correctness with their higher-level descriptionsAll boxes (and all procedures) describe functionsFormal proofs of correctness can be performed (but often informal proofs are done, instead)

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Verification of Sequence

Given a high-level function [f] for statement: do [g]; [h] od

Does [g] followed by [h] compute the same function as [f]?

Example:[f](x) = 2 * x + 7[g](x) = 2 * x[h](x) = x + 7

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Verification of Selection

Given a high-level function [f] for statement:

if <cond> then[g]else[h]fi

1. Whenever <cond> is true, does [g] compute the same function as [f]?

2. Whenever <cond> is false, does [h] compute the same function as [f]?

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Verification of Iteration

Given a high-level function [f] for statement:

while <cond> do[g]od

1. Whenever <cond> is true, does [g] followed by [f] compute the same function as [f]?

2. Does the loop always terminate?3. Whenever <cond> is false, does the empty

function compute the same function as [f]?

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Usage Testing

Develop an operational profile of use

Generate random tests that fit the probabilities

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Example

FunctionUsage Probability

Distribution Interval

Update 32% 0-31

Delete 14% 32-45

Query 46% 46-91

Print 8% 92-99

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Test Generation

TestRandom Numbers Test Cases

1 29, 11, 47, 52, 26, 94

U, U, Q,Q, U, P

2 62, 98, 39, 78, 82, 65

Q, P, D,Q, Q, Q

3 83, 32, 58, 41, 36, 17

Q, D, Q,D, D, U

4 36, 49, 96, 82, 20, 77

D, Q, P,Q, U, Q

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Industrial Use

Used in a few areas of IBM

Used by some military contractors

Tried at NASA

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Software Engineering Laboratory (SEL)

Joint program of NASA Goddard Space Center, Computer Sciences Corporation, and the University of Maryland

Conduct experiments and case studies on new software technology

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SEL Experience

First trial at University of Maryland controlled experiment (10 experiment teams,

5 control teams FORTRAN 1.5 KLOC

3 case studies at Goddard flight-dynamics ground support systems FORTRAN 40 KLOC, 22 KLOC, 160 KLOC

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SEL Results – University Experiment

Cleanroom teams use fewer computer resources satisfy requirements more successfully make higher percentage of scheduled

deliveries

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SEL Results – Goddard

More effort spent in design

Better reliability of final product

Smaller projects achieve higher productivity, but large project just average

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Summary

Cleanroom may be an effective method for achieving higher reliability

Requires some culture change (no debugging)

Still being investigated by researchers and practitioners

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References

Victor Basili and Scott Green, "Software process evolution at the SEL", IEEE Software 11(4), 58-66, July 1994.