287 Chapter 13 Internet of Things: A Context-Awareness Perspective Davy Preuveneers and Yolande Berbers Contents 13.1 Introduction ...................................................................................... 288 13.1.1 Software Architecture and the Internet of ings ..................... 288 13.1.2 Context Awareness and the Internet of ings ...........................289 13.1.3 Convergence as a Key Enabler for the Internet of ings ...........290 13.2 State-of-the-Art on Context-Aware Computing for Nonintrusive Behavior .......................................................................290 13.2.1 A Definition of Context ............................................................. 291 13.2.2 Using RFID to Sense Context.................................................... 291 13.2.3 Requirements for Representing and Exchanging Context ..........292 13.3 Trends in Context-Aware Computing within Service Orientation ..........296 13.3.1 Context-Enabled Service Oriented Architecture and the Semantic Web................................................................296 13.3.2 Context-Enabled Service Delivery Platforms ..............................297 13.4 Service Provision in a Context-Aware, Converged Service Architecture ............................................................................................299 13.4.1 Context Management as an Enabling Service ........................... 300 13.4.2 Conveying Context and Distributed Storage .............................. 301 AU5281_C013.indd 287 12/3/07 12:39:07 PM
Transcript
287
Chapter 13
Internet of Things: A Context-Awareness Perspective
13.1 IntroductionThenextwaveintheeraofcomputingwillbeoutsidetherealmofthetraditionaldesktop.IntheInternetofThings�paradigm(IoT)[22],everythingofvaluewillbeonthenetworkinoneformoranother.RadiofrequencyIDentification(RFID)andsensornetworktechnologieswillgiverisetothisnewstandard,inwhichinfor-mation and communication are invisibly embedded in the environment aroundus.Everydayobjects, suchascars,coffeecups, refrigerators,bathtubs,andmoreadvanced,looselycoupled,computationalandinformationserviceswillbeineachothersinteractionrangeandwillcommunicatewithoneanother.Largeamountsofdatawillcirculateinordertocreatesmartandproactiveenvironmentsthatwillsig-nificantlyenhanceboththeworkandleisureexperiencesofpeople.Smartinteract-ingobjectsthatadapttothecurrentsituationwithoutanyhumaninvolvementwillbecomethenextlogicalsteptopeoplealreadyconnectedanytimeandanywhere.WiththegrowingpresenceofWiFiand3GwirelessInternetaccess,theevolutiontoward ubiquitous information and communication networks is already evidentnowadays.However,fortheInternetofThingsvisiontosuccessfullyemerge,thecomputingcriterionwillneedtogobeyondtraditionalmobilecomputingscenariosthatusesmartphonesandportables,andevolveintoconnectingeverydayexistingobjectsandembeddingintelligenceintoourenvironment.Fortechnologytodis-appearfromtheconsciousnessoftheuser,theInternetofThingsdemands:(1)asharedunderstandingofthesituationofitsusersandtheirappliances,(2)softwarearchitectures andpervasive communicationnetworks toprocess and convey thecontextualinformationtowhereitisrelevant,and(3)thecomputationalartifactsintheInternetofThingsthataimforautonomousandsmartbehavior.Withthesethreefundamentalgroundsinplace,smartconnectivityandcontext-awarecompu-tationviaanything,anywhere,andanytimecanbeaccomplished.
13.1.1 Software Architecture and the Internet of ThingsAnysoftwarearchitecture,designedtobedeployedwithinthesettingoftheInter-net of Things, will need to foresee the increasing heterogeneity of devices andnetworks,andwillhavetoprovideforvaryinguserandapplicationrequirementswithindiversecontextsofserviceprovision.Itwillbeessentialfornewarchitectures
�Internet of Things refers to a ubiquitous network society in which a lot of objects are“connected.”
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tointegratethelatesttechnologiesintheareasofsoftwareandhardwareinordertoassimilateasmuchaspossibledataandservicesavailableintheenvironmentoftheuser.Asserviceintegration-relatedtaskswillremaininevitable,itisnosurprisethattheindustryisaimingforsoftwaresolutionsthatmakethisintegrationamoretrac-tableactivity.Theevolutiontowardintegratedserviceorientationisalreadyemerg-ingintheongoingconvergenceofWebservicesandtelecommunicationservices[21].Service-OrientedArchitecture(SOA)[27]isanarchitecturalstylethatenablesthecomposition of applications by using loosely coupled and interoperable services.Theseoftentransaction-basedservicesaredescribedandexposedusingopenstan-dards—inthecaseofWebservicesusingWSDL,SOAP,andBPEL[40]—thatareindependentoftheunderlyingprogramminglanguageandplatform.Thetelecom-municationsworldhasembracedtheServiceDeliveryPlatform(SDP)architecturalapproachtoenablemoreflexiblecommunicationandcollaborationservicesbyevolv-ingtoall-IP(InternetProtocol)networksforthedeliveryofmultimedia-enabledandlocation-orpresence-awareservices.Duetoitsevent-drivencommunicationpara-digm,anSDPdiffersfromthepreviousarchitecturalstyleinthataSOAtypicallydoesnotneedtomeetanyreal-timedemandsforitsdata-drivencommunication.BothSOAandSDPsoftwarearchitecturescommonlyprovisionserviceorchestra-tioncapabilitiesbyexposing their servicesusingopen standards, andoften sharebuildingblockstohandlenoncorefunctionalities,suchasauthentication,identitymanagement,andbilling.Asaresult,convergedservicesbringustheflexibleinterac-tionsfromtheWebserviceparadigm,nicelyintegratedwiththecommunicationandcollaborationservicesfromthetelecommunicationsworld.KeytothesuccessoftheInternetofThingswillbetheabilitytoconnecteverydayobjects,includingRFIDtagsandotherexistingresources,tosuchservice-orientedarchitecturessothatitwillleadtoanoverallflexiblearchitecturethataimstocreateapleasantuserexperienceattheworkplace,inpublicareasaswellasinthehomeenvironment.
13.1.2 Context Awareness and the Internet of ThingsContextawarenessplaysanimportantroleintheaforementionedsoftwarearchi-tectures toenableservicescustomizationaccordingtothecurrentsituationwithminimalhumanintervention.Acquiring,analyzing,andinterpretingrelevantcon-textinformation[11]regardingtheuserwillbeakeyingredienttocreateawholenewrangeofsmartentertainmentandbusinessapplicationsthataremoresupport-ivetotheuser.Althoughcontext-awaresystemshavebeenintheresearchepicenterformorethanadecade[32,33],theabilitytoconveyandselectthemostappropri-ate information toachievenonintrusivebehavioronmultiuser-convergedserviceplatformsinmobileandheterogeneousenvironmentsremainsasignificantman-agementchallenge.InteroperabilityatthescaleoftheInternetofThingsshouldgobeyondsyntacticalinterfacesandrequiresthesharingofcommonsemanticsacrossallsoftwarearchitectures.Italsodemandsaseamlessintegrationofexistingcom-putationalartifacts(hardwareandsoftware)andcommunicationinfrastructures.
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Onlythencancontextinformationbesuccessfullysharedbetweenhighlyadaptiveservices across heterogeneous devices on large-scale networks that consider thisinformationrelevantfortheirpurposes.
13.1.3 Convergence as a Key Enabler for the Internet of Things
Insummary,theInternetofThingsisallaboutconvergence,fromconnectedcom-puting using RFID and sensor technology to digital content and context-awareservices,anobservationthatwasalsomadeinthedigital lifestylechapterofthedigital.life ITU Internet Report 2006[23].ThesuccessoftheInternetofThingswillnotsomuchdependonthedevelopmentofnewtechnologies,butmoresooncon-nectingandintegratingexistingresources,rangingfromsmall-scaleobjects,suchasRFIDtags,uptolarge-scalesoftwaresystemsthatservethousandsofclientsatatime.Thegoalistocreateasoftwarearchitecturethatenablesobjectstoexchangeinformation through the Internet to achievenonintrusivebehavior and custom-izedservices.Partofthearchitecture’sresponsibilityistomakesurethatrelevantinformationarrivesattherightplaceinawaythattherecipientunderstandswhatitreceives.Here,weinvestigatehowsuchanarchitecturecanbedesignedbyinte-gratinginnovativescientificresultsfromrelatedresearchdomainswithindustrialtechnologiesandpracticeswithaproventrackrecord.
In section 13.2, we describe the current state-of-the-art in context-awarecomputinganddiscuss thegoals,motivation, and requirements thatdefine theactualneedforcontextawareness inorder toachieveabetterunderstandingofthe concepts involved. We review the trends for its use in converging service-oriented architectures in section 13.3. To illustrate the benefits of introducingcontext awareness as one of the underpinning fundamentals of the Internet ofThings,wealsoelaborateonourrecentresearchactivitiesatthearchitecturallevelinsection13.4.Itillustrateshowtointegrateexistingtechnologiesandcomputa-tionalartifactssupportingcontextawarenessasanenablingserviceamongstotherbuildingblocksinanoverallservice-orientedarchitectureforuseinhomeappli-ances and online consumer services. By not reinventing the wheel, but insteadleveraging on solid foundations from the software and knowledge engineeringdomains, nothing stands in the way for applications targeting the Internet ofThingsmodeltobecomeasuccess.
13.2 State-of-the-Art on Context-Aware Computing for Nonintrusive Behavior
13.2.1 A Definition of ContextManyauthorsinitiallydefinedcontextinformationbyenumeratingtypesofinfor-mationrelatedtotheuserorapplicationenvironmentthatseemedrelevant.ThetermcontextwasfirstusedbySchilitandTheimer[32]toreferto“location,identi-tiesofnearbypeopleandobjects,andchangestotheseobjects.”Brown,Bovey,andChen[6]havedefinedcontextas“location,identitiesofthepeoplearoundtheuser,thetimeofday,season,temperature,etc.”Ryan,Pascoe,andMorse[31]referredtocontextas“theuser’slocation,environment,identity,andtime.”Dey[10]listed“theuser’semotionalstate,focusofattention,locationandorientation,dateandtime,objectsandpeopleintheuser’senvironment”aselementsbeingpartofthedefinitionofcontext.Astheuseofenumerationstodescribecontextwastoolim-ited to analyze whether certain information could be classified as context, Deyetal.[1]providedthefollowingmoregeneralandwidelyaccepteddefinitionthatencompassesthepreviousones:
Contextisanyinformationthatcanbeusedtocharacterizethesitu-ationofentities(i.e.,whetheraperson,placeorobject)thatarecon-sideredrelevanttotheinteractionbetweenauserandanapplication,includingtheuserandtheapplicationthemselves.Contextistypicallythe location, identity and state of people, groups and computationalandphysicalobjects.
Therefore, context involves relevant information on real world entities. Thisinformationneedstobedescribedinastructuredandeasilyextensiblemodeltofacilitatethesharingofcollectedinformation.Therefore,itisimpossibletolimitcontextinformationtoafixedsetofattributesorproperties.
13.2.2 Using RFID to Sense ContextRFID is an emerging technology for embedding sensing capabilities in every-day objects[39] and is gaining momentum as a popular means for automatic
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identification and tracking in supply chain management. Each tag contains auniqueIDnumberthatcanbereadbyanRFIDreader.ActiveRFIDtagshavetheirownpowersupplytotransmittheirsignal,whilepassiveonesusetheelectricalcurrentinducedintheantennaduringreceptionoftheincomingradiofrequencysignalemittedbytheRFIDreader.Thepresenceofaninternalpowersupplyhelpstoextendtherangeofoperationandtheamountofinformationthatcanbetrans-mitted.Themajorityofpassivetagstypicallyhaveanywherefrom64or96bits(torepresentanelectronicproductcode(EPC)[13]asshowninFigure13.1)to1kbofnonvolatileEEPROMmemory,whileactivetagshavebattery-backedmemoriesashighas128kbandmore.
Figure 13.1 A passive RFID tag having 96 bits of memory to represent an EPC number.
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introduceafixedstructureandallowtoexpressmorecomplexrelations,suchasassociations. These types of models are frequently used to capture user profiles(e.g.,FriendofaFriend(FOAF)[5])anddeviceprofiles(e.g.,CompositeCapabli-ties/Preferences Profile (CC/PP)[24] and User Agent Profile (UAProf)[16]). Sofar,ontologies,providingaspecificationofaconceptualization[17],seemtobethemostpromisingway togowhenmodelingcontext[37,7,18,38].Ontologiesarewellknownintheknowledgerepresentationcommunitytomodelconceptsandtherelationshipsthatholdamongthemandtheirsemanticinterpretationisuniversallyaccepted.Figure13.2illustratesagraphicalrepresentationofthe
Activity Role
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Environmental ConditionTimeLocation
has Time
has Location
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requires Platformprovides Software
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has Activity has Role has Mood
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ONTOLOGY–BASED MODELING OF CONTEXT–AWARENESS
Figure 13.2 The CoDAMoS context ontology that models the user, platform, service, and environment concepts and interrelationships with other relevant classes.
Comprehensivedomaincoverageandterminology:Anopencontextspec-ificationlanguageshouldmakeavailableaterminologythatprovidesappro-priatecoverageandacomprehensiverepresentationofadomaininordertomodelmostof the concepts and termsneeded fordescribing entities in aparticular domain. Concepts may be modeled with multiple synonymousrepresentationsandmayhavehierarchicalrelationshipstootherconcepts.Semantic nonambiguity and expressiveness: Information semanticsinvolvetheuniforminterpretationofaconcept.Thisrequiresastrictsup-port fornonambiguity in the specification language to ensure that eachconceptintheterminologyhasonlyonemeaning.Semanticexpressivenessistheabilitytoeasilyenhancetheknowledgedomainusingthesemanticprimitivesofthespecificationlanguage.Moreadvancedsemanticspecifi-cationlanguagesforcontextprovidesupporttomodelspecializationandinheritancerelationships,aggregation,dependenciesandconstraints,etc.Processingcomplexity:Somelanguagesrequirequitecomplexprocessingstepsforboththedataacquisitionandprocessing(e.g.,reasoningandinfer-ence)parts.Forexample,contextmodelsusingResourceDescriptionFrame-work(RDF)[4]orOWL[20]mayrefertootherremotelyavailablecontextmodels todetail thesemanticsandrelationshipsofconceptsbeingreused.This,ofcourse,isagoodthingasitimprovesknowledgesharing,interoper-ability,anduniversalinterpretation.However,italsoincreasesthecomplexitytoprocesscontextmodels.AstheInternetofThingstargetscomputationalartifactsofdifferentshapesandsizes,anappropriatebalanceshouldbefoundbetweenprocessingcomplexityandlanguageexpressiveness.Specification language interoperability:There isnoone single specifi-cationthatwillsolveallissueswithrespecttocontextprovisioninginanopenfashion.Forsomepurposes,theuseofaparticulardomain-specificlanguagemayalreadybe sopervasive that this in itselfwouldbeoneofthereasonsnottoreimplementthesameconceptsinanothermoregenericspecificationlanguage.Therefore,theeaseofreusingandintegratingdiffer-entdedicatedspecificationlanguagesisalsoanimportantconcern.
Manyopenspecificationlanguagesaregeneralpurposedescriptionlanguages(e.g.RDF[4] and OWL[20]), while others target a very specific domain. Forexample, dedicated languages and specification formalisms have been proposedto model the hardware and software characteristics of mobile handheld devices(e.g., CC/PP[24] and UAProf[16]). Regarding RFID technology, it was onlyrecently(2007)that theElectronicProductCodeInformationServices (EPCIS)standard[14] was ratified, effectively providing an XML schema binding and abindingtoSimpleObjectAccessProtocal(SOAP)overHTTPviaaWSDL(WebServiceDescriptionLanguage)totheEPCinformationonanRFIDtag.Someofthesedomainspecificformats,suchasUAProf,builduponageneralpurposelan-guagelikeRDF,asillustratedinFigure13.3.Notonlydoestheexpressivenessof
13.3.1 Context-Enabled Service Oriented Architecture and the Semantic Web
ServiceOrientedArchitecture(SOA)representsthecurrentstate-of-the-artinsoft-warearchitecturefortherapiddeploymentofnewservices.Itenablesthecreationofnewservicesorapplicationsbyconnectingtogetherexistingservicesandpro-posesfunctionstomanagetheservicelifecycle.ThemainmotivationbehindSOAforacompanyistocreateabusiness-alignedarchitecturetobetterreacttochang-ingcustomers’needs.Ifthemarketchanges,newservicescanbecreatedbyreusingexistingservicesandbydevelopingnewserviceswhereneeded.ASOAalsoenablesacompanytoleveragepreviousinfrastructureinvestments,byexposinglegacyser-vicesas traditional services in thearchitecture:ASOAincreasescode reuseandmodularity.
A service-oriented architecture targeting thegrowingproliferationofRFID-equippeddeviceswithintheInternetofThings,whereeachcomputationalartifactmayaccessmultipleserviceswithindiversecontexts,willbecomeadauntingtaskwithoutproperidentitymanagement.Theuseofcontextawarenesshelpstopro-videmorefine-grainedaccesscontroltoinformationandservices.OneillustrationofthistrendispresentedintheworkofArdagnaetal.[3]whereposition,move-ment,andinteractionpredicatesareintroducedinauthorizationpoliciesrelyingonGroupeSpécialMobile(GSM)/third-generation(3G)technologiestoachieveloca-tion-constrainedaccess.WiththeintroductionoftheE-passport,fittinginRFIDinformationintopolicyenforcementrulesis justasmallstep.FormanagingtheinformationflowintheInternetofThings,contextawarenessisbecomingamuchlargerconcerninSOAthanitisatthemoment.
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Another emerging trend is coming from the Semantic Web community.AlthoughtheWSDL[8]hasbeenverysuccessfulasasyntacticspecificationlan-guagetointeractwithWebservicesusingdifferentbackendenvironments,itdoesnotprovideanysupportforaconsistentinterpretationoftheWebservicecontent.Theuseofontologieshasalreadygainedmuchattentionforthesemanticmodelingofcontext,asillustratedinFigure13.4.Theapplicationofontologiesisalsofind-ingitswayinnewWebservicespecifications,includingOWL-S[25],METEOR-S[34],WSDL-S[2],WSMO[9,15],andothers,toaugmentservicedescriptionsinordertoautomatetheirdiscovery,composition,andinvocationinpervasivecom-puting environments. The services, that were previously only described by theirpublicinvocationinterfaces,arenowenrichedwithmachine-interpretableseman-ticsby referring toand reasoningonestablishedontologies that encapsulate themeaningoftheservice.Also,fortheInternetofThings,theuseofontologieswithinthearchitecturemayhelptomakesenseofitall,forboththecontextinformationaswellastheservicesbeingoffered.
13.3.2 Context-Enabled Service Delivery PlatformsDuringthelastdecade,thetelecommunicationsworldhastransformedradicallyduetotheshifttowardInternet-styleinfrastructuresforthedeliveryofmultimedia-enabledcommunicationservices.Today’sverypopular,IP-basedVoIP(VoiceoverInternetProtocol)systemsaretheresultoftheevolutionfrommonolithicandiso-latedinfrastructurestoservicedeliveryplatformsthatadopttheIPnetworkastheir
CONTEXT–AWARENESS AND THE SEMANTIC WEB “LAYER CAKE”
Context–awareapplications for theInternet of Things
Context Content
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Figure 13.4 Aligning context awareness and standardized specifications for the Internet of Things along the Semantic Web “layer cake” (Courtesy of T. Berners-Lee).
SIP Specific Event Notification: This is an extension that allows SIPnodestorequestinformationfromremotenodes.Beingagenericpackage,itcanbeusedtonotifyandconveyanycontextualchangetowhomitmayconcernwhensuchaneventhasoccurred.PresenceInformationDataFormat(PIDF):ThisisanXMLdocumentthat provides presence information about a presentity, including statusinformation and optionally contact addresses, timestamps, and textualnotes.AnexampleisgiveninFigure13.5.
n
n
PRESENCE INFORMATION DATA FORMAT
<?xml version=“1.0” encoding=“UTF–8”?><presence xmlns=“urn:ietf:params:xml:nspidf” entity=“pres:[email protected]”> <tuple id=“123456”> <status> <basic>open</basic> </status> <contact priority=“0.75”>tel:+32987654321</contact> <timestamp>2007–03–15T17:26:21Z</timestamp> <note>I am busy right now ...</note> </tuple></presence>
Figure 13.5 Specifying presence within SIP using the basic PIDF format.
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Rich Presence Information Data Format (RPID): This format buildsuponPIDFandaddselementsthatprovideadditionalinformationaboutthepresentity�(location,mood,activity,etc.)anditscontacts.OtherrelatedSIPstandards:CommonProfileforPreference,CommonProfileforInstantMessaging,ContactInformationinPresenceInforma-tionDataFormat,TimedPresenceExtensionstothePIDF,etc.
Wecanobservethat,giventhelistofSIPspecificationsanddraftrecommenda-tions,presence isan importantconcern in telecommunications. In supplychainmanagement, where RFID technology typically has a strong foothold, presenceandavailabilityplayanimportantroleaswell.Althoughproductswillnotdirectlycommunicatetheirpresencetoallinterestedpartiesbythemselves,itisclearthattheflexibilityoftheSIPsignalingprotocolmakesitanexcellentcandidatetodeliverreal-timeandup-to-datecontextinformationtoallsubscribers.
13.4 Service Provision in a Context-Aware, Converged Service Architecture
Interoperability between Web service-and telecommunication-oriented architec-turesisacomplexissue.AserviceinSOAisessentiallytransaction-basedandreliesonanarchitecturethatoftenbuildsuponthefunctionalityofanenterpriseservicebus(ESB)toprovidemessagebrokering,routing,datatranslation,andtransforma-tion.AservicewithinaSDPneedstodealwithamultitudeofpoint-to-pointcon-nectionsandshort-livedeventsthatmustbegenerated,propagated,andprocessedwithalowlatencytoguaranteeaminimalqualityofservicelevel.TheproposedarchitecturefortheInternetofThings,therefore,integratesbothkindsofservicesatthesessionlevelbecausethatiswheretheinteractionbetweentwoservicesstartsandwhereitcanbenefitthemostfromcontextinformation.AsWebservicesandtelecommunicationservicesusesimilarthoughcompetingstandardsforinforma-tionexchange;anenterpriseservicebusisusedinsidethearchitecturetomanagethemessageconversionandroutingduringasession.Ahigh-levelconceptualover-viewofthearchitectureisgiveninFigure13.6.
The goal of introducing context awareness in a converged service-orientedarchitectureistosimplifythediscoveryofinformationaboutanentitywhenthisinformationcannotbeeasilysearched,isnotmadeexplicitintherequiredformat,orneedsaggregationwithother information sourcesbefore it canbeused.Ourcontextmanagementsystem[29]representsitselfasanenablingserviceinthecon-vergedservice-orientedarchitecture,inasimilarwayasbillingandpolicyenforce-mentdo.Neitheroftheseservicesprovideanyfunctionalitydirectlytotheclient,butdo so toother enabling and end-user services. Similar tobilling andpolicy
�Presentity: A presentity(presenceentity)providespresenceinformationtoapresenceservice(RFC2778).
13.4.1 Context Management as an Enabling ServiceContextmanagement from an enabling service perspective involves the followingfunctionalrequirements,nomatterwhetherthecontextinformationisusedlocallyorneedstobedeliveredtoaremotecomputationalartifactsomewhereonthenetwork.
13.4.2 Conveying Context and Distributed StorageAfter having consolidated context information from various acquisition systems(sensors,people,devices,etc.)andremoteinputchannels(services,databases,etc.),the collected informationmaybe selected fordistribution to remote subscribers(people, services, devices). When information is gathered from or needs to be
n
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ONLINE MUSICSTORE
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Figure 13.7 Building blocks of the context awareness-enabling service.
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delivered to a remote entity, choicesneed tobemadeonwhere contextwill bestored.Theobviouschoicewouldbeclosetotheareawhereitisconsideredrelevant,andperhapsbeduplicated ifnecessary. Ifcontext is stored locallyonthedevicethatsensedtheinformation,itisreadilyavailableandroundtripsonthenetworktoretrievetheinformationareavoided.However,iftheinformationisalsousefulforotherparties,thenitmakessensetostoretheinformationremotelyonareposi-torythatismoreeasilyaccessible.Thefollowingconcernsaretakenintoaccountwhetherinformationshouldbestoredlocallyorremotely:
Scopeofrelevance:Certaininformationcanberelevantonlyforcompu-tationalartifactsthatinteractinparticularwithlocalservices.Anobviousexample is the intelligenthomeenvironmentwherethe informationthatphotovoltaiclightsensorsinthehouseprovide,isnotofinterestoutsidethehomeenvironment.Informationsensitivity:TrackinginformationretrievedfromRFIDtagscouldbeofinteresttomultiplepartiesonthenetworkandbemadeavail-ableonaremoteserverforfurtheranalysis.Personalinformation,ontheotherhand, is keptprivate onpurpose andonly sharedwith authorizedentities.Althoughprivacyissuesareanimportantconcernincontext-awarecomputing,wewillnotgointodetailhereasprivacyisalreadycoveredtoalargeextentinotherchaptersandinthespecializedliterature.Information currentness and period of relevance: Static and profiledinformationislikelytoremainvalidforlongerperiods.Forexample,thepositionoffixedbeaconsisinformationthatishighlysuitedfordistribu-tion,assynchronizationdoesnotneedtooccuroften.Volatileinformationontheotherhand,suchasthecurrentsystemload,maynolongerbeaccu-rateorrelevantwhenitisfinallyremotelystoredinarepository.Cachingforinformationreachability:Ifsomesensorinformationcanbeobtainedquiteeasily,thenstoringtheinformationmaynotbeworthwhile.However,assomeappliancesmighthavenodirectconnectiontocontextsensorsthatprovideusefulinformation,arepositorywithstandardSOAPor SIP interfaces can collect and make the information accessible to allinterestedparties.Exploitinginformationhistory:Insomecases,anappliancemightwanttoexploitthehistoricvaluesofacertaincontextattributeinordertoderivenewinformation.Forexample,bytrackingthecurrentposition,thetraveleddistancecanbederivedandusedtoreimbursetravelingexpenses.Althoughtheinformationisnolongeraccurate,itisstillconsidereduseful.
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13.5 Context Awareness from RFID to the End-User in the Internet of Things
The digital lifestyle chapter of the digital.life ITU Internet Report 2006[23]describesseveralfuturisticscenariostowardcontext-awareservices.Wewillbrieflysummarizethemandthendiscusshowourconvergedservice-orientedarchitecturewouldaccomplish the tasks in these scenarios if thearchitecturewouldbe fullyimplementedanddeployedonalargescale.
Mostoftheabovescenariosrelyonlocationawarenessoftheuser.ThislocationcouldbeobtainedusingRFIDorBluetoothtechnologyinstalledinthecellphoneof theclient,or fromaGPSnavigationsysteminthecar.Thetypesof locationinformationisdifferent(identifier,MACaddress,latitude,andlongitude)andwilllikelyneedtobeconvertedfirstbythecontext-awareness-enablingservicebeforeitcanbeusedbyoneoftheend-userservices.Presenceawarenesscomesintoplayinscenario1and5.Thecontext-awareness-enablingserviceverifiesfirstusingtheSIPprotocolifthepersoninquestionisavailableandwhatkindofcommunicationhecurrentlyprefers,andthensendsamessagetothecorrespondingaddress.Userprofilesareusedbytheshopownertolinkanidentitywithpreviouslypurchasedgoods,andatclientsidetostorethehomeandworkaddress,thesizeofyourshirt,SIP contact information, etc. Some context information conversion is needed toconvertthecurrentlocationtoafour-letterMETARweatherstationidentifiertogetthelocalweatherreportathomeandatwork.Sensortechnologyisusedtochecktheamountof fuel, tocheck thebody temperature, todetectmovementsat thefrontdoorofthehouse,etc.ThesecondscenariocouldbeanorchestrationofWebservicesthataresemanticallydescribedusingOWL-S.AfterusingSOAPtosend
TheabovescenariosprovideamixtureofWebserviceandtelecommunicationserviceorchestrations,contextawareness,RFIDandsensortechnology,localandremoteservices,SIPandSOAPcommunication,andsoon.Althoughareal-lifedeployment of the architecture has not been done to test the feasibility, we areconfidentthatourcurrentarchitecturecanaccomplisheachofthesetasks.Alltherequirementshavebeencoveredintheprevioussectionsandinteroperabilitysup-portisbuiltintothearchitecturetomakethesescenarioswork.
13.6 ConclusionsTheInternetofThingsisallaboutconvergenceandintegrationofthelatestadvance-mentsintheresearchareasofsoftwareandhardwarewithindustrialtechnologiesinventedmanydecadesago.Indeed,althoughRFIDisoneofthecornerstonesofthisnewcomputerparadigmandbecomingmorewidespreadnowadaysduetoitslowproductioncosts,itsinventionstemsfromtheWorldWarIIperiodwhenitwasdevelopedformilitarypurposes.Inthischapter,wehavehighlightedtwoconcernsofgreatimportancefortheInternetofThings.Onecomesfromthesoftwareengi-neeringdomain,namelytheuseofagoodsoftwarearchitecturestyleforthedesignofanysoftwaresystem,andanotheroneisrelatedtotheknowledgeengineeringdomain and deals with context awareness, also one of the goals of the InternetofThings.Researchcarriedoutinthecontext-awarecomputingdomainaimstocreateapleasantuserexperienceattheworkplace,inpublicareasaswellasinthehomeenvironmentbysimplifyinghumaninteractionswitheverydayservicesandmakingthemlessintrusive.WehavediscussedhowRFIDtechnologycancontrib-utetocontextawarenessasawaytoidentifyandlocateeverydayobjectsaswellashumans,forthatmatter.
Wehave arguedwhy serviceorientation is a good architectural style for theInternetofThingsbecauseit leveragesexistingapplicationsbyexposingthemastraditional services in thearchitecture. It increases reuseandmodularity, speed-ingup the integrationeffort.Wehaveproposeda servicearchitecture thataimstobridgecontextawarenesswiththeworldsofWebservicesandtelecommunica-tionservices.Bothapplicationdomainshavecontributedintheirownwaytothedevelopment of context-aware services by standardizingdescription formats andprotocolstoconveyrelevantinformationtowhomitmayconcern.Standardizationisgood,onlyifnotforthefactthatmanyofthemaresimilarandcompetingwithoneanother.Forthisreason,wehaveintroducedcontextawarenessasanenablingservice in the architecture, leveraging information from both areas at a centralplace. The context-awareness-enabling services is responsible for the acquisition,
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13.7 Open IssuesDespitethegreatpotentialofcontextawarenessfortheInternetofThings,therearestillsomehurdlestocrossthatmayslowdowntheadoptionofRFIDandotheremergingtechnologies.Oneoftherepercussionsofcontext-awarecomputingistheinvasionofone’sprivacy.Whiletheaimistoincreaseconveniencebyreducingtheamountofinteractionsbetweenusersanddevices,itisofutmostimportancetonotlosesightofprovidingalevelofusercontrolinordertosetthemindsatease.OnlywhenpeoplearepartoftheInternetofThingsandfeelincontrolwillthisnewwayofcomputinghaveachanceofbeingwidelyadopted.
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