Managing Trade-Offs in Adaptable Software Architectures

400 Pages·2016·14.16 MB·English

by  Ivan Mistrik

Managing Trade-offs in
Adaptable Software
Architectures
Managing Trade-offs in
Adaptable Software
Architectures
Edited by
Ivan Mistrik
Nour Ali
Rick Kazman
John Grundy
Bradley Schmerl
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Contributors
N. Ali
University ofBrighton, Brighton, United Kingdom
M. Abdelrazek
DeakinUniversity, Melbourne, VIC, Australia
S. Andrade
Federal Instituteof Education,Science,and Technology ofBahia;Federal University ofBahia,
Salvador, Bahia, Brazil
F. Arcelli Fontana
University ofMilano-Bicocca,Milan, Italy
P. Avgeriou
University ofGroningen,Groningen, Netherlands
R. Bahsoon
University ofBirmingham, Birmingham, UnitedKingdom
N. Bencomo
Aston University, Birmingham, United Kingdom
A. Bennaceur
The Open University, Milton Keynes, UnitedKingdom
P. Boxer
BoxerResearch Limited,London, United Kingdom
J. Ca´mara
Carnegie Mellon University, Pittsburgh, PA,United States
K. Canavera
GeorgeMason University, Fairfax, VA,UnitedStates
R. Capilla
Rey Juan CarlosUniversity, Madrid, Spain
C. Carrillo
Polytechnic University ofMadrid, Madrid, Spain
R. deLemos
University ofKent, United Kingdom;CISUC,University of Coimbra, Portugal
N. Esfahani
GoogleInc, MountainView, CA,United States
D. Garlan
Carnegie Mellon University, Pittsburgh, PA,United States
J. Grundy
DeakinUniversity, Melbourne, VIC, Australia
xv
xvi Contributors
A.Ibrahim
Deakin University, Melbourne, VIC, Australia
R.Kazman
CarnegieMellonUniversity, Pittsburgh,PA; University of Hawaii, Honolulu,HI, United States
^
R.Macedo
Federal University ofBahia, Salvador, Bahia, Brazil
S.Mahdavi-Hezavehi
University of Groningen,Groningen, Netherlands; Linnaeus University, V€axj€o,Sweden
S.Malek
University of California,Irvine, Irvine, CA, United States
I. Mistrik
IndependentSoftwareResearcher, Heidelberg, Germany
G.A. Moreno
CarnegieMellonUniversity, Pittsburgh,PA, United States
H.A. M€uller
University of Victoria, Victoria, BC, Canada
B.Nuseibeh
TheOpenUniversity,MiltonKeynes,UnitedKingdom;Lero—TheIrishSoftwareResearchCentre,
Limerick,Ireland
O.Ozcan
BilkentUniversity, Ankara, Turkey
P.Potena
Fondazione BrunoKessler, Trento, Italy
C.Raibulet
University of Milano-Bicocca, Milan, Italy
M. Salama
University of Birmingham, Birmingham, United Kingdom
B.Schmerl
CarnegieMellonUniversity, Pittsburgh,PA, United States
H.Sozer
Ozyegin University, Istanbul, Turkey
G.Tamura
Universidad Icesi, Cali, Colombia
B.Tekinerdogan
Wageningen University, Wageningen,The Netherlands
N.M. Villegas
Universidad Icesi, Cali, Colombia
D.Weyns
Linnaeus University, V€axj€o, Sweden
About the Editors
IvanMistr´ıkisaresearcherinsoftware-intensivesystemsengineering.Heisacomputerscientistwho
isinterestedinsystemandsoftwareengineeringandinsystemandsoftwarearchitecture,inparticular:
lifecyclesystem/softwareengineering,requirementsengineering,relatingsoftwarerequirementsand
architectures, knowledge management in software development, rationale-based software develop-
ment, aligning enterprise/system/software architectures, value-based software engineering, agile
software architectures, and collaborative system/software engineering. He has more than 40 years’
experience in the field ofcomputer systems engineeringas an informationsystems developer, R&D
leader, SE/SA research analyst, educator in computer sciences, and ICT management consultant. In
the past 40 years, he has been primarily working at various R&D institutions in United States and
Germany and has done consulting on a variety of large international projects sponsored by the
ESA, EU, NASA, NATO, and UN. He has also taught university-level computer sciences courses
insoftwareengineering,softwarearchitecture,distributedinformationsystems,andhuman-computer
interaction.Heistheauthororco-authorofmorethan90articlesandpapersininternationaljournals,
conferences,books,andworkshops.Hehaswrittenanumberofeditorialsforspecialissuesandedited
books.Hehasalsowrittenover120technicalreportsandpresentedover70scientific/technicaltalks.
Hehasservedinmanyprogramcommitteesandpanelsofreputableinternationalconferencesandor-
ganized a number of scientific workshops. He was the lead-editor of nine books between 2006 and
2015: Rationale Management in Software Engineering, Rationale-Based Software Engineering,
Collaborative Software Engineering, Relating Software Requirements and Architecture, Aligning
Enterprise/System/Software Architectures, Agile Software Architecture, Economics-Driven Software
Architecture, RelatingSystem Quality andSoftware Architecture, and Software Quality Assurance.
NourAlihasbeenaPrincipalLecturerattheUniversityofBrightonsinceDec.2012.SheholdsaPh.D.
inSoftwareEngineeringfromthePolytechnicUniversityofValencia-SpainforherworkinAmbients
in Aspect-Oriented Software Architecture. She is a Fellow of the UK Higher Education Academy
(HEA). Her research area encompasses service-oriented architecture, software architecture, self-
adaptation,andmobilesystems.In2014,theUniversityofBrightongrantedheraRisingStarsaward
in Service Oriented Architecture Recovery and Consistency. She is currently the Principal
InvestigatorfortheRoyalSocietyNewtongrant,“AnAutonomicArchitecturalApproachforHealth
Care Systems,” and is the Knowledge Supervisor for the Knowledge Transfer Partnership project
for migrating legacy software systems using architecture centric approach. She has also been the
Principal Investigator for an Enterprise Ireland Commercialisation Project in Architecture Recovery
and Consistency and co-investigator in several funded projects. Dr. Ali serves on the Programme
Committeeforseveralconferences(e.g.,ICWS,ICMS,andHPCC)andjournals(e.g.,JSS,orJIST).
Shehasco-chairedandco-organizedseveralworkshopssuchastheIEEEInternationalWorkshopon
Engineering Mobile Service Oriented Systems (EMSOS) and the IEEE Workshop on Future of
Software Engineeringfor/inthe Cloud. Shewasthe co-editor oftheJSS Special Issueonthe Future
ofSoftwareEngineeringfor/intheCloudpublishedin2013andhasco-editedthreebooksincluding
AgileandLeanService-OrientedDevelopment:Foundations,Theory,andPractice,publishedin2012.
xvii
xviii About the Editors
SheistheApplicationTrack chairforInternationalConference onWeb Services(ICWS2016). Her
personal website is:http://www.cem.brighton.ac.uk/staff/na179.
John Grundy is Professor of Software Engineering and Pro-Vice Chancellor ICT Innovation and
Translation at Deakin University, Australia. Previously he was Dean of the School of Software
and Electrical Engineering and also Director of the Swinburne University Centre for Computing
and Engineering Software Systems (SUCCESS). Before coming to Swinburne, he was Head of
Department for Electrical and Computer Engineering at the University of Auckland, New Zealand.
His teaching is mostly in the area of team projects, software requirements and design, software
processes, distributed systems, and programming. His research areas include software tools and
techniques, software architecture, model-driven software engineering, visual languages, software
securityengineering,service-basedandcomponent-basedsystemsanduserinterfaces.Hehasauthored
over 300 publications and supervised over 50 Ph.D. and Masters by research students. He provides
consulting work for a range of companies which have included, among many others, Data61, DST
Group, Mailguard, Thales Australia, CA Labs, XSol Ltd, Orion Health Ltd, Peace Software Ltd,
and Whitecloud Systems Ltd.
Rick Kazman isaProfessor atthe University ofHawaii and aPrincipal Researcher atthe Software
Engineering Institute of Carnegie Mellon University. His primary research interests are software
architecture, design and analysis tools, software visualization, and software engineering economics.
Kazman has created several highly influential methodsand toolsfor architecture analysis, including
theSAAM(softwarearchitectureanalysismethod),theATAM(architecturetradeoffanalysismethod),
theCBAM(cost-benefitanalysismethod),andtheDaliandTitantools.Heistheauthorofover200
publications,andco-authorofseveralbooks,includingSoftwareArchitectureinPractice,Designing
SoftwareArchitectures:APracticalApproach,EvaluatingSoftwareArchitectures:MethodsandCase
Studies,andUltra-Large-ScaleSystems:TheSoftwareChallengeoftheFuture.Hispublicationshave
beencitedover16,000times,makinghimoneofthemostcitedauthorsinallofsoftwareengineering.
BradleySchmerlisaPrincipalSystems Scientist intheInstituteforSoftware Research at Carnegie
MellonUniversity,USA.Hehasbeeninvolvedinresearchinself-adaptivesystemsforover20years,
startingwithhisPh.D.atFlindersUniversityinSouthAustralia,whichinvestigatedusingconfiguration
management techniques to manage dynamically changing systems. He was a Lecturer at Flinders
UniversityandanAssistantProfessoratClemsonUniversityinSouthCarolinabeforejoiningCarnegie
Mellonin2000.Heisinvolvedinresearchusingsoftwarearchitecturemodelsasabasisforreasoning
aboutself-adaptingsystems,includingusingutilitytheorytoselectappropriatestrategiesthatbalance
multiplequalityandbusinesspriorities.Hehasco-authoredoveradozenjournalandconferencepapers
on self-adaptation, co-organized the Second Workshop on Self-Organizing Architectures in 2011,
co-editedtheSpecialIssueon“StateoftheArtinSelf-AdaptiveSystems”oftheJournalofSoftware
and Systems in 2012, and was program chair for the 2015 International Symposium on Software
Engineering for Adaptive andSelf-ManagingSystems.
Foreword by David Garlan
Theideaofasystemthatadaptsitselfwhileitisrunningisasoldasthenotionofcomputation.Butfor
manyyearsthecomplexityofcreatingsuchsystemshardlyjustifiedtheirvalue.Systemstypicallyran
in predictable, stable environments, and their requirements and fault models were fairly well
prescribed.
Butoverthepastcoupleofdecades,manythingshavedrivensystemdesignerstoreconsidertheprop-
ositionofself-adaptingsoftwaresystems.Todaysystemsmustfunctionincomplexenvironmentsbuiltout
ofinfrastructure,components,services,andothersystemsthatarenotunderdirectcontroloftheoriginal
system’sdevelopers.Requirementsmaychange.Environmentschange,particularlyinthepresenceofmo-
bility.Systemconfigurationsmustbeoptimizedtosatisfymultiple(oftenconflicting)qualitygoalsdictated
bybusinesscontext.And,atthesametime,theneedtodeploysystemswith24/7availabilityhasmovedout
ofthenichesystemcategory(telephonesystem,energygrid,etc.)intomainstreamsoftware.
Aboutadecadeandahalfago,peoplebegantorealizethattoaccountforthisnewreality,itwas
important to understand how to make systems more resilient, more malleable, and more extensible,
withoutcompromisingquality,costofdevelopment,andcostofdeployment—and,significantly,with-
outtakingsystemsoffline.Oldsolutionsofsimplythrowingmoresystemadministratorsattheproblem
werebecomingincreasinglycost-prohibitive.Andengineeringfaulttoleranceandsystemreconfigura-
tion directlyinto the system was leading tounsustainable complexity.
Whatemergedwasablossomingofanewfocusonthesoftwareengineeringofself-adaptivesys-
temsthatcouldrisetothechallengesofmoderncontexts.Almostsimultaneouslythereemergednew
venuesfordiscussingsuchissues:theACMWorkshopsonSelf-HealingSystems(WOSS),theInter-
national Conference on Autonomic Computing (ICAC), the international workshop on self-adaptive
software(IWSAS),andothers.And,withinthedomainofcommercialsystems,webegantoseemyriad
new (albeit special-purpose) mechanisms for adaptation: automated server monitoring and repair in
Internet-basedsystems,adaptiveperformancethroughcloudcomputingplatforms,andmicro-services
to supportrapid,and frequent,deployment offunctional enhancements.
Additionally,amajoradvanceinourthinkingaboutsuchsystemsemergedthroughtherecognition
thatonewaytoaddressthechallengesofself-adaptationwastotakeacontrolsystemsperspectiveon
theproblem.Specifically,asystemcouldbemadeself-adaptivebyaddingsensorstomonitoritsrun-
timestate,actuatorstochangeitatruntime,andaseparatereasoningmechanismtodecidewhenitis
appropriatetoadaptthesystem,andhowbesttodoso.Thiswasfamouslyreferredto(insomecircles)
as the MAPE-K loop, ormonitor-analyze-plan-execute usinga shared base of knowledge.
This perspective (among others) helped researchers and developers consider the architectures of
self-adaptivesystemsasfirst-classareasofstudy.AndwhiletheoverallMAPE-Kcontrolarchitecture
tendstoencompassmostsuchefforts,numerousnewchallengesemergeinordertogetthedetailsright.
Monitoring:Whatdoesitmeantohavesufficientsituationalawareness,andwhatcanonedowhen
such informationisunavailable orhighlyuncertain? How can onesift through large volumesof
low-level system observations toderive higher-level views ofsystem behavior andstate?
Analysis:Howcanasystemdeterminewhenadaptationisnecessary?Howcanitidentifythepartof
the system thatneeds tobe adapted? Howdo you prioritizethe possible problems that need to
beaddressedwhenseveralaredetected?Towhatextentshouldthesystemfocusonfaults,andto
xix
xx Foreword by David Garlan
what extent on homeostatic improvement? What are appropriate measuresof system quality that
takeintoaccountmultipledimensionsofconcern(e.g.,cost,performance,security,availability)?
How do yourecognize “softer” problems,wherethe system isoutof balance with respect to
competingqualityattributes (e.g., sacrificingdeployment cost to improve performance)?
Planning: How can one determinean appropriate adaptationstrategy that considers the inherent
trade-offs between different quality dimensions that might be affected? How can one balance
the need for rapid response tocriticalproblems,while stillsupportlonger-range system
improvement?Howcanoneprovideassurancethatadaptationwillmakeasystembetter,andnot
worse? Howcan one provide guarantees about coverage ofpotential problems?How can one
buildplanningmechanismsthatareproactiveinanticipatingproblemsandcorrectingthembefore
they do damage? How doyou reasonabout uncertainty, giventhe fact that we may notknow
preciselythe state ofthe system,environment,or even the outcomes ofrepair actions?
Execution:Howcanyoubuildsystemssotheiractuationinterfaceprovidesmoreflexibilitytothe
adaptiveprocess? How can yousupportconcurrent adaptations ofthe same system?
Knowledge:What kinds ofinformationare mostusefultothe adaptationprocess? How can you
strike a balance between abstractviews ofthe system and detailed enough informationtomake
informeddecisionsabout adaptation? Can cooperating adaptivesystemsshare knowledgeto
improvethe adaptation behavior of the ensemble?
Inadditiontothesekindsofchallenges,newforcesintechnologyareraisinginterestingquestionsabout
positioning adaptive systems in today’s ecosystems. For example, increasingly computing systems
must work in the context of physical devices and technologically rich environments. Such systems,
sometimes referred to as the Internet of Things or cyber-physical systems, raise the question of
how to combine what we have learned about software adaptation with more traditional disciplines
of physical control. As another example, systems today must take into account the capabilities of
the humans that interact with them. Humans may be clients of the adaptive system, but also might
be viewed as components in the overall adaptation process. Indeed, in principle humans can serve
inanyoftheMAPE-Kroles—forexample,providingcontextualinformationtothesystem,assisting
with adaptation, or performing physical actions toachieve some desired result.
Itisclearthatmuchremainstobedone,andwhatwedoknowtodaywillneedtoevolvewiththe
shiftinglandscapeoftechnologyanditsuseinourworld.Thechaptersinthisbookspantheentirefield:
fromengineeringofadaptivesystems,toreasoningaboutthem,toexploringtheiruseinemergingfron-
tiers.Despitethisdiversity,however,acrossallofthesechaptersisabroadconcernwiththequestionof
balancingtrade-offs.Themomentyougodown thepathofadaptation,youarefacedwithquestions
abouthowbesttoreconcileconflictinggoalsandrequirements:oftimelyresponsewithoptimalrepair,
of multiple system qualities that must be balanced to provide overall utility, of automated versus
human-assisted adaptation, of localized versus distributed control, of human-assisted versus stand-
alone adaptation. Balancing trade-offs thus provides a common theme underlying these chapters,
and,infact,anyserioustreatmentofself-adaptation.Assuch,thisbookprovidesbothabroadperspec-
tiveanddeepexplorationofmanyoftheseissues,servingasanexcellentstartingpointforsomeone
whowantstoknowmoreaboutthefield,aswellforresearchersandpractitionerswhowantamorein-
depth examination ofrecentresearch and itspotential.
David Garlan
Foreword by Nenad Medvidovic
Behold the Golden Age of Software Architecture
Inthe mid-to-late1990s,Ihadthe fortune ofwitnessingagreatdeal ofactivityandinnovationthat,
today,issometimesreferredtoasthe“goldenage”ofsoftwarearchitectureresearch.Asacommunity,
weweretryingtounderstandthephenomenaunderlyingsoftwaresystems’architectures,developab-
stractionstocapturethosephenomena,constructmodelstoembodytheabstractionsproperlyandef-
fectively,analyzethemodelsforinterestingandimportantproperties,and,finally,figureouthowto
implement systems that would inherit all of the positive and none of the negative characteristics we
encounteredalongtheway.Thisresultedinaseemingwhirlwindofnotations,techniques,tools,pat-
terns,styles,andreferencearchitectures.Itwasanincrediblyexcitingandfuntimeifyouwereasoft-
ware architecture researcher. The rest, asthey say, hasbeen history.
Anissuethatemergedsomewhatmoreslowlyanddeliberatelybycomparisontotheabovewasarchi-
tecturaladaptation.Onequestionwasalwaysthere:Onceyoubuildthesystem,youwillinevitablychange
it,sowhatdoesthatdotothearchitecture?Thatquestion,however,turnedouttohaveamorecompelling
counterpart:Whatdoyouhavetodotoandwiththearchitecturetomakeitsupportthechangeinthesys-
tem?Asaresultofmultipleyearsofinvestigatingthisquestion,severalcolleaguesandIcameupwithwhat
wehavesincenamed(hopefullyforobviousreasons)the“figure8”model,shownbelow.
xxi