Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
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Chapter2<br />
Background<br />
Inthischapterweelaborateonsome<strong>of</strong>theconceptsbrieflyintroducedin<br />
Chapter1. Inparticular,wediscusss<strong>of</strong>twareevolution,s<strong>of</strong>twarearchitecture,<strong>and</strong>model-drivenengineeringinthelight<strong>of</strong>theresearchquestions<br />
weposedpreviously.<br />
2.1 S<strong>of</strong>tware<strong>Evolution</strong><br />
Engineeringdisciplinesaretypicallybasedonuniversal,scientificlaws<strong>and</strong><br />
principles.Alsointhediscipline<strong>of</strong>s<strong>of</strong>twareengineeringanumber<strong>of</strong>such<br />
lawshavebeendiscovered.Endres<strong>and</strong>Rombach[2003]giveanoverview.A<br />
few<strong>of</strong>themostwidelyacknowledgedlawsweredefinedbyLehman[1978]<br />
<strong>and</strong>areconcernedwiththechange<strong>of</strong>s<strong>of</strong>twaresystemsovertime:s<strong>of</strong>tware<br />
evolution.Theyarebasedonempiricalobservations.Thefirsttwo<strong>of</strong>these,<br />
so-called,laws<strong>of</strong>s<strong>of</strong>twareevolutiondynamicsarestatedinTable2.1on<br />
thefollowingpage.<br />
ThegraphinFigure2.1onthenextpageillustratesbothlawsbyplottingameasureforsizeagainstameasureforcomplexity<strong>of</strong>embedded<br />
copiers<strong>of</strong>twaredevelopedbyOcé. Itshowsatrend<strong>of</strong>increasingsize<strong>and</strong><br />
complexityforthesubsequent(i.e.,intime)revisions<strong>of</strong>thes<strong>of</strong>tware.<br />
S<strong>of</strong>twareevolvesbecause<strong>of</strong>variousreasons.Thes<strong>of</strong>twaresystems(programs)referredtointhes<strong>of</strong>twareevolutionlawsare,forinstance,affected<br />
bychangesintherealityreflectedintheirspecification[Lehman,1980].<br />
Suchchangesarecausedbychangesinstakeholderobjectivesortothe<br />
environment. Anexample<strong>of</strong>theformerareadditionalormodifiedstakeholderrequirements.<br />
Anexample<strong>of</strong>thelatter,inthecase<strong>of</strong>embedded<br />
systems,arechangestohardware. Asaresponseas<strong>of</strong>twaresystemrequiresadaptivemaintenance.Obviously,theusefulness<strong>of</strong>as<strong>of</strong>twaresystemdecreasesifsuchmaintenancetasksarenotperformed.<br />
Othertypes<br />
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