EVOLVINGBUILDINGBLOCKSFORDESIGNUSINGGENETIC ENGINEERING A FO(3)

Abstract. This paper presents a formal approach to the evolution of a representation for use in a design process. The approach adopted is based on concepts associated with genetic engineering. An initial set of genes representing elementary building blocks

6JohnS.GeroANDVladimirA.

Kazakov

Figure5.Thesetofadditionalassemblyrulesforhandlingcompositebuildingblocks.thatthisuniquecausecanbedirectlyrelatedtotheorganism’sgeneswhichap-pearinastructuredforminitsgenotype.Geneticengineeringinconcernedwithlocatingthosegeneswhichproducethe tnessunderconsiderationandinmodify-ingthosegenesinsomeappropriatemanner.Thisisnormallydoneinastochasticprocesswhereweconcentrateonpopulationsratherthanonindividuals.

Organismswhichperformwell(orbadly)inthe tnessofinterestaresegreg-atedfromtheseorganismswhichdonotexhibitthat tnessordosoonlyinamin-imalsense.Thisbifurcatesthepopulationintotwogroups.Thegenotypesoftheformerorganismsareanalysedtodeterminewhethertheyexhibitcommonchar-acteristicswhicharenotexhibitedbytheorganismsinthelattergroup(Figure6).Iftheyaredisjunctive,thesegenesareisolatedonthebasisthattheyarerespons-iblefortheperformanceofthe tnessofinterest.Innaturalgeneticengineeringtheseisolatedgenesareeithertheputativecauseofpositiveornegative tness.Ifnegativethentheyaresubstitutedforby“good”geneswhichdonotgeneratethenegative tness.Iftheyareassociatedwithpositive tnesstheyarereusedinotherorganisms.Itisthislaterpurposewhichmapsontoourareaofinterest.

Onecaninterprettheproblemof ndingthetargetedsetofbuildingblocksasananalogofthegeneticengineeringproblem: ndingtheparticularcombin-ationsofgenes(representingelementarybuildingblocks)ingenotypeswhichareresponsibleforthepropertiesofinterestofthedesignsandregularusageofthesegeneclusterstoproducedesignswithdesiredfeatures.

Abstract. This paper presents a formal approach to the evolution of a representation for use in a design process. The approach adopted is based on concepts associated with genetic engineering. An initial set of genes representing elementary building blocks

EvolvingBuildingBlocksforDesignUsingGeneticEngineering

7

‘‘good’’ genotypes‘‘bad’’ genotypes

Figure6.Thegenotypesofthe“good”membersofpopulationallexhibitgenecombinations,X,whicharenotexhibitedbythegenotypesofthe“bad”members.Thesegenecombinationsaretheonesofinterestingeneticengineering.

2.Buildingblocks

Thus,weestablishthatdifferentbuildingblocksde nedifferentdesignstatespaces(whichare,intheirturn,thesubsetsoftheentirebasicdesignspace).Moreform-allyweassumethatforthedesignspaceofinterestasetofcompositebuildingblocksexistswhichissuf cienttobuildanydesignofinterestfromit(orwhicharesuf cienttobuildasigni cantpartofanyofthesedesignsofinterest).

Wesearchforthesebuildingblocksusingtheconsequenceoftheassumptionmadeintheintroductionaboutfrequenciesofcompositecomponentsusage:onav-eragethesamplingsetofdesignswiththedesiredcharacteristics(the“good”ones)containsmoreofsuchcompositebuildingblocksthanthesamplingsetofdesignsthatdonothavethesecharacteristics(the“bad”ones).Insomecasesitiseventrueinadeterministicsense-thatonlythedesignswhichcanbebuiltcompletelyfromsomesetofcompositebuildingblockspossesstheobjectivecharacteristics,alltherestoftheentirebasicstatespacedoesnothavethem.Onecaneasilycomeupwithcorrespondingexamples.

Inthenextsectionwedescribeanevolutionaryalgorithmwhichgenerates“good”and“bad”samplingsetsusingthecurrentsetofbuildingblock(setofelementaryblockatthebeginning)andusegeneticengineeringconceptstodeterminenewcompositeblockswhichareclosertothe“targeted”onesthanthecurrentsetofbuildingblocks.Thesetwostepsproceedincyclewhilethe“good”samplingsetconvergestothesamplingsetfromthedesireddesignstatespaceandthesetof

Abstract. This paper presents a formal approach to the evolution of a representation for use in a design process. The approach adopted is based on concepts associated with genetic engineering. An initial set of genes representing elementary building blocks

8

JohnS.GeroANDVladimirA.

Kazakova

bFigure7.Theassembly(transformation)rulesusedintheexample.

complexbuildingblockscomescloserandclosertothetargetedset.

Ifthebasicassumptionaboutmorefrequentuseofsomecompositebuildingblockstogeneratetheparticularclassofdesignsisnottrueforsomeproblemthenthetargetedrepresentationforthisproblemdoesnotexistandthealgorithmwhichisproposedbelowwillnotgenerateanimprovedrepresentationbutwillbeequi-valenttothealgorithmforsolvingtheroutinedesignproblem(GeroandKazakov,1995)andwillsimplygeneratetheimproveddesigns.

Ifthesequenceofassemblyactionsiscodedasarealvectorthentheproblemof ndingthecomplexbuildingblocksbecomestheproblemof ndingthekeypatternsinthecodingvector-thecombinationsofcodeswithinitwhicharelikelytobeassociatedwiththepropertyofinterestinthedesigns.Thevastarsenalofpatternrecognitionmethodscanbeusedtosolvethisproblem.Essentiallytheyarejustsearchmethodsforsubsetsinacodingsequencewhichonaveragearemorefrequentlyobservedinobjectswithdesiredcharacteristicsthanintherestofthepopulation.

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