Re: ENSC 440 Design Specification for an RFID Smart Fridgewhitmore/courses/ensc305/projects/2011/14desi.pdf · Re: ENSC 440 Design Specification for an RFID Smart Fridge ... Catalog

November 20th, 2011 Dr. Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby, British Columbia V5A 1S6 Re: ENSC 440 Design Specification for an RFID Smart Fridge Dear Dr. Rawicz: The document attached outlines the design specification for Cyber-Flux Innovations’ RFID Smart Fridge. Our team is designing a smart refrigerator which will keep track of its contents and provide useful information to customers through a website and mobile phone application. Our design specification document applies to the proof-of-concept prototype we are currently developing. Design improvements for future models of the RFID Smart Fridge are discussed, but will not be implemented in this stage of development. This document will direct the development and testing process of the prototype. Our team is comprised of four talented undergraduate students from Simon Fraser University: Lead Integration Manager: Damir Jungic (Electronics stream), Lead Hardware Design: Mitchell Joblin (Biomedical stream), Lead Software Design: Steven Verner (Computer stream), and Lead Project: Renato Pagliara (Biomedical stream). If you have any questions or concerns regarding our functional specifications, please do not hesitate to contact us at [email protected]. Sincerely,

Renato Pagliara Renato Pagliara Project Lead Cyber-Flux Innovations Enclosure: RFID Smart Fridge Functional Specification

RFIDSMARTFRIDGE

DESIGNSPECIFICATION

Project Team: Damir Jungic Mitchell Joblin Steve Verner Renato Pagliara

Contact Person: Renato Pagliara

[email protected]

Submitted to: Dr. Andrew Rawicz – ENSC 440 Mike Sjoerdsma – ENSC 305 School of Engineering Science Simon Fraser University

Issued Date: November 20th, 2011

CYBER‐FLUXINNOVATIONS’SMART‐FRIDGEFUNCTIONALSPECIFICATIONSNov2011

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EXECUTIVESUMMARY

The design specification of the RFID Smart Fridge provides a set of detailed descriptions of the design and development of our proof-of-concept prototype system. The design specifications in this document apply solely to the proof-of-concept prototype. While the specifications in this document might deviate from the features of the system as described in the document RFID Smart Fridge Functional Specification (Pagliara, Jungic, Joblin, & Verner, 2011), we have added features which were not previously described which address key issues of power and performance. We have integrated a temperature and humidity sensor into the in-Fridge hardware to provide users with the ability to monitor the conditions inside the fridge in real-time. At the same time, the addition of a reel switch located on the fridge’s door allows us to maintain the power consumption of the system to a minimum while ensuring we keep basic network functions running. This document outlines the design of the RFID Smart Fridge and provides justification for our design decisions. The RFID Smart Fridge System development has been divided into four modules as well as system integration: In-Fridge Hardware, Backend Server, Server Features and Smartphone App. The in-Fridge hardware located within the fridge reads RFID tags inside of the fridge using a RFID reader/writer unit. The reading of the fridge’s contents is triggered by the closing of the fridge door. The information from the tags is then sent to the server through a Local Area Network (LAN) using a WiFi module. This process, together with the temperature/humidity readings from the sensor, is coordinated through an Arduino microcontroller. The Backend Server saves tag information received from the Hardware Unit. The server then extracts the barcode information from each tag and runs it through a database to obtain the products’ name and nutritional information. Once the information from the products has been obtained, the user can observe the contents of their fridge through either a web browser or through their iPhone. As well, users can automatically generate a grocery list based on the history of their fridge’s contents and consumption prediction algorithms. Finally, nutrition models, calculated from the nutritional information retrieved from a product catalogue database, will allow the users to quantify the level of nutrition for each item inside the fridge. The iPhone will leverage all the processing power of the backend server and will work as a web client which will help costumers navigate through the many features offered by the Smart Fridge System. Design decisions, including selection of hardware, are justified throughout this document. General software program process flow is also included. Further, a description of the test plan for the system and its subcomponents is included. Finally, a discussion about the safety of RFID technology is presented to ensure this critical aspect of product development is not overlooked. The expected completion date for the RFID Smart Fridge project is December 06, 2011.


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ACRONYMS&ABBREVIATIONS

1‐D One‐Dimensional

App Application

HTML HyperTextMarkupLanguage

HTTP HyperTextTransferProtocol

ISO InternationalOrganizationforStandardization

LAN LocalAreaNetwork

LED Light‐emittingDiode

MB Megabyte

RFID RadioFrequencyIdentification

Temp Temperature

UID UniqueHardwareIdentification

UML UnifiedModelingLanguage

UPC UniversalProductcode

WiFi Wireless‐Fidelity

GLOSSARY

Radiofrequencyidentificationsystem:Anautomaticidentificationanddatacapturesystemcomprisedofoneormorereader/interrogatorsandoneormoretranspondersinwhichdatatransferisachievedbymeansofsuitablymodulatedinductiveorradiatingelectromagneticcarriers(AIMGlobal,2010).

Transponder:AnelectronicTRANSmitter/resPONDER,commonlyreferredtoasaTag[sameasabove].

UniqueHardwareIdentification(UID):throughoutthisdocument,wewilldefineUIDasaneight

hexadecimalcharacterslongnumberwhichuniquelyidentifiesatransponder.

UniversalProductCode(UPCorEAN):barcodesymbologywidelyusedinNorthAmerica,fortrackingtradeitemsinstores.Itsmostcommonform,theUPC‐A,consistsof12numericaldigits,whichare

uniquelyassignedtoeachtradeitem.AlongwiththerelatedEANbarcode,theUPCistheonlybarcodeallowedforscanningtradeitemsatthepointofsale,perGS1standards(GS1,2011).


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TABLEOFCONTENTS

ExecutiveSummary ..................................................................................................................................... 3

Acronyms&Abbreviations .......................................................................................................................... 4

Glossary ....................................................................................................................................................... 4

Tableofcontents ......................................................................................................................................... 5

Listoffigures ............................................................................................................................................... 7

1 Introduction......................................................................................................................................... 7

Scope........................................................................................................................................................ 8

IntendedAudience................................................................................................................................... 8

2 SystemSpecifications .......................................................................................................................... 8

RFIDTechnology....................................................................................................................................... 9

RFIDTechnologyandSafety................................................................................................................... 10

3 OverallSystemDesign ....................................................................................................................... 10

4 In‐FridgeHardware............................................................................................................................ 13

RFIDreader/writer: ................................................................................................................................ 14

Microcontroller ...................................................................................................................................... 15

WiFiModule........................................................................................................................................... 16

Temperature/Humiditysensor .............................................................................................................. 16

ISO15693RFIDProtocol ......................................................................................................................... 16

Microcontroller‐RFIDreader/writerCommunication ............................................................................ 16

Power ..................................................................................................................................................... 17

Casing ..................................................................................................................................................... 17

5 BackendServer .................................................................................................................................. 18

ObjectHierarchy .................................................................................................................................... 18

AddingandRemovingItems .................................................................................................................. 20

Serialization............................................................................................................................................ 22


6

Client’sResponsibilities.......................................................................................................................... 23

6 ProductCatalog ................................................................................................................................. 24

7 Communication ................................................................................................................................. 25

BackendServices.................................................................................................................................... 26

In‐FridgeHardwaretoBackendServerCommunication........................................................................ 28

MobileApptoBackendServerCommunication .................................................................................... 29

WebServertoBackendServerCommunication .................................................................................... 30HTMLAssembly ................................................................................................................................. 30Time‐DependentContent .................................................................................................................. 30Plotting .............................................................................................................................................. 31

8 SoftwareSystem................................................................................................................................ 31

Auto‐GeneratedGroceryList ................................................................................................................. 31AlgorithmInterface............................................................................................................................ 31Component1 ..................................................................................................................................... 32Component2 ..................................................................................................................................... 32Component3 ..................................................................................................................................... 32Component4 ..................................................................................................................................... 33Component5 ..................................................................................................................................... 33Summary............................................................................................................................................ 33

NutritionMetricSystem......................................................................................................................... 36NutritionalProfilingModel ................................................................................................................ 36SystemDescription ............................................................................................................................ 36NutritionItemClass ........................................................................................................................... 36NutritionMetricsClass ...................................................................................................................... 36ConstructNutritionItem ................................................................................................................... 36TopFiveLists...................................................................................................................................... 37AverageNutritionalValueofList ....................................................................................................... 37ItemsInRange ................................................................................................................................... 37NutritionalValueversusTime ........................................................................................................... 37

9 MobileApplication ............................................................................................................................ 41

Overview ................................................................................................................................................ 38

MobileAppSystemDesign .................................................................................................................... 40

10 Testing ............................................................................................................................................... 41

SimulatedFridgeSystem........................................................................................................................ 41

CommunicationTesting ......................................................................................................................... 43BackendServerTesting...................................................................................................................... 43


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In‐FridgeHardwaretoBackendServerCommunicationTesting....................................................... 44iPhoneApplicationtoBackendServerCommunicationTesting........................................................ 44WebServertoBackendServerCommunicationTesting ................................................................... 44

11Conclusion.......................................................................................................................................... 44

12References ......................................................................................................................................... 45

LISTOFFIGURES

Figure1:SystemOverview .......................................................................................................................... 9Figure2:SystemOverview ........................................................................................................................ 11Figure3:In‐FridgeHardwarelocationwithinthefridge ........................................................................... 13

Figure4:In‐FridgeHardwaresubsystemdiagram..................................................................................... 14Figure5:GeneralISO15693request.......................................................................................................... 16Figure6:UMLDiagramofCoreBackendServerClasses ........................................................................... 20

Figure7:AddingtotheInFridgeSetProcessFlow ..................................................................................... 21Figure8:JavaXMLBinding(JAXB)Workflow ............................................................................................ 22Figure9:CommunicationOverview .......................................................................................................... 26

Figure10:AutoGeneratedGroceryListAlgorithm .................................................................................. 35Figure11:NutritionalMetricStructure ..................................................................................................... 38Figure12:MobileApplication‐InMyFridgeView ..................................................................................... 39

Figure13:MobileAppClassHierarchy ...................................................................................................... 40

LISTOFTABLES

Table1:RFIDcommerciallyavailablereader/writerunitsandtheircharacteristics(Ward&vanKranenburg,2006) ..................................................................................................................................... 15

Table2:DescriptionofItemTypeFields .................................................................................................... 18Table3:PathsMadeAvailablebyServer................................................................................................... 26Table4:PathsandtheirQueries ............................................................................................................... 27

LISTOFLISTINGS

Listing1:SimpleUPCRequestExample..................................................................................................... 25Listing2:SimpleUPCResponseExample ................................................................................................... 25

Listing3:ExampleofXMLSentfromIn‐FridgeHardwaretoBackendServer ........................................... 28


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1 INTRODUCTION

TheRFIDSmartFridgeisasmarthomeappliancewhichbesidesfunctioningasaregularfridge,itkeeps

trackofitemstaggedwithRFIDtranspondersplacedinsidethefridgeandprovidescustomerswithextrainformationabouttheirproducts,theirnutritionalfactsandtheirfridge’scontentshistory.ThisdocumentdescribesthetechnicaldetailsbehindtheSmartFridgesystem.Theinformationhasbeen

dividedintothesystem’sfourmaincomponents:in‐Fridgehardware,backendserver,serverfeaturesandsmartphoneapp.Thedocumentalsoincludesatestplanfortheintegrationofallfourcomponentsintothesystem.

ScopeThisdocumentspecifiesthedesignoftheRFIDSmartFridgesystemandexplainstowhatdegreehave

thefunctionalrequirementsasdescribedinRFID Smart Fridge Functional Specification(Pagliara,Jungic,Joblin,&Verner,2011)beenmet.Atthesametime,newfeaturesnotlistedinthepreviouslymentioneddocumenthavebeenaddedtothesystemandareexplainedindetailinthisdocument.The

designspecificationencompassestherequirementsfortheproof‐of‐conceptsystemandapartialsetofrequirementsforaproductionmodel.

IntendedAudienceThedesignspecificationisintendedforusebythemembersofCyber‐FluxInnovations.Leadengineerswillrefertothespecificationsasguidelinesforthedevelopmentofthesystembutin

casetheydeemitnecessarytheywillmodifythesespecificationstoensureallrequirementsaremetinthefinalproduct.Thisproductwillalsobeusedduringthetestingphasetoensuretoconfirmthe

correctbehaviouroftheSmartFridgesystem.

2 SYSTEMSPECIFICATIONS

TheRFIDSmartFridgewillconsistofamodifiedfridgethatdetectsitemsbeingputinortakenoutvia

theirRFIDtag(usinganRFIDreader).ThereaderthensendsthetaginformationtoaserverviaaLANwheretheinformationwillbeprocessedandmadeavailabletotheuserthroughasimplemobileapplicationandwebsiteasseeninthediagrambelow.Theserverwillprocessthislargeamountof

informationandmakeitavailableinasimple,convenient,usefulmannerthroughitsinterfacestogivetheuseralistofthefridge’scurrentcontents,alistoffoodswhichwillexpiresoon,anautomaticallygeneratedgrocerylistbasedontheuser’seatinghabitsandsomesimpleandrelevantnutritional

informationaboutthefridge’scontentsandrecenthistory.


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Figure1:SystemOverview

RFIDTechnologyRadioFrequencyIdentification(RFID),asitsnameimplies,makesuseofradiowavestotransferinformationfromatransponder(inourcase,atag)toareader,withthepurposeofidentifyingthetransponderandthustheobjectitisattachedto.AnRFIDsystemconsistsofthreeelements:an

antenna,atransceiverwithadecodertointerpretthedataandatransponderthathasbeenprogrammedwithinformation.Theantennaemitsradio‐frequencysignalsinarelativelyshortrange.TheRFradiationprovidesameanofcommunicatingwiththetransponder(theRFIDtag)andprovides

theRFIDtagwiththepowernecessarytocommunicate(inthecaseofpassivetransponders).

ThankstothetransmissionofpowerthroughtheRF‐signals,RFIDtagsdonotneedtocontainbatteries,andremainusableforyears.WhenanRFIDtagpassesthroughthefieldofthescanningantenna,itdetectstheactivationsignalfromtheantenna.That"wakesup"theRFIDchip,andittransmitsthe

informationonitsmicrochiptobepickedupbythescanningantenna.RFIDtagscanbeeitheractiveorpassive.ActiveRFIDtagshavetheirownpowersource;thismeansthat

thereadercanbemuchfartherawayandstillgetthesignal.PassiveRFIDtags,however,donotrequirebatteries,andcanbemuchsmallerandhaveavirtuallyunlimitedlifespan.RFIDtagscanbereadinawidevarietyofcircumstances,wherebarcodesorotheropticallyreadtechnologiesareuseless.Thetag

neednotbeonthesurfaceoftheobject(andisthereforenotsubjecttowear).Thereadtimeistypicallylessthan100milliseconds.DependingontheRFIDreader,largenumbersoftagscanbereadatonce.Forsimplercheaperreaders,itemsshouldbereaditembyitem(technovelgy.com,2010).


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RFIDTechnologyandSafetyThesafetyofunderlyingtechnologiesplaysakeyroleinhigh‐leveldesigndecisions.Indeed,theveryplausibilityoftheSmartFridgeSystemrequiresthattheunderlyingtechnologynotharmpeopleorthe

foodthatthesystemcomesintocontactwith.Itisnecessarytoconsidertwoprimarysafetyissues:doesRFIDtechnologyinterferewithfoodanddoesitinterferewithpacemakersorsimilarelectricalmedicaldeviceswornusers.

IthasbeenobservedthatRFIDtagsoperatingatlowfrequenciescanaffecttheoperationofpacemakers

(USFoodandDrugAdministration,2010).However,thelargerreadrangeofhigh‐frequencyreadersmakethempreferablefortheSmartFridgeSystem.Higher‐frequencysignalsareroutinelyfilteredbywornmedicaldevices,andthereforeposenoknownrisktodevicebehaviour.TheSmartFridgeSystem

willthereforenotharmuserswhorelyonwornorimplantedmedicaldevices.

StudiesobservingtheeffectsofNon‐IonizingFields,suchasthosecreatedbyRFIDreaders,onlydemonstrateshort‐termeffects(suchasheating)(RFID4SMEandtheEuropeanUnion,2008).Further,itisworthnotingthatanElectro‐MagneticField(EMF)isonlypresentwithinthefridgewhiletheRFID

readerisreadingtags.Tagsareonlyreadafterthefridgedoorisclosed.Further,thereadingthecontentsoftheentirefridgeonlytakesseconds.TheexposureofthefoodwithinthefridgetoanEMFisthereforeextremelyminimal.TheSmartFridgeSystemthereforeisnotharmfultothefoodwithwhichit

comesintocontactwith.

3 OVERALLSYSTEMDESIGN

Ahigh‐leveloverviewoftheSmartFridgeSystemispresentedinFigure2.Fromthepointofviewof

costumers,theRFIDSmartFridgesolutionhasthreemaincomponents:theIn‐FridgeHardware,theBackendServerandtheSmartphoneApp.Eventhoughtheproductcatalogueisnotpartoftheserver(itisastandalonesoftwareserviceavailablethroughtheweb),fromcostumer’spointofviewitappearsas

iftheserverisperformingtheserviceswhichbelongtotheproductcatalogue.


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Figure2:SystemOverview

TheIn‐FridgeHardwareisinstalledwithinthefridgeandisinchargeofobtaininginformationabouttheproductsplacedinsidethefridgethroughtheRFIDtags.Theservertakesthatinformationand,uponrequestfromtheuserthroughthewebpage,allowsuserstocheckthecontentsofthefridge,generate

grocerylistsandcheckthenutritionalvalueofpresentandpastproductswithinthefridge.Inthesameway,theusercanaccessthesethreefeaturesthroughtheSmartphoneApp.Finally,theSmartphoneAppoffersafourthfeaturewherecostumerswillbeabletoenteritemsintothesystemthatdonothave

anRFIDtagbyeitherenteringthenameoftheproduct(forleftovers)orbyscanningtheUPCbarcode(forproductswhichdonothaveanRFIDtag)andattachingaRFIDread/writetagtotheproduct.

Thesystemthus,hastwogeneralcases:

Productswithabuilt‐inRFIDtag:

Inthiscasetheinformationflowsinalinearfashionthroughthesystem.Whenthedoorofthefridgecloses,thein‐FridgehardwarescansthefridgeforRFIDtags.Afterreadingallthetagswithinthefridge,

theinformationisenclosedinamessageandsenttotheserver.

ProductswithoutaRFIDtag:


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InthiscasetheuserstartstheflowofinformationbyenteringthenameorscanningtheUPCbarcodeoftheitemthroughtheSmartphoneApp.TheuserthenattachesaRFIDtagtotheproduct/leftoverand

insertsitintothefridge.Theflowofinformationfromthereonwardsisthesameasinthefirstcase.

ThisdocumenthasbeendividedintosectionsdedicatedtotheexplanationofthemainsubsystemswithintheSmartFridgesolution.ThedesignoftheIn‐FridgeHardware,BackendServer,ProductCatalogue,SoftwareSystemandtheSmartphoneAppcomponentsofthesystemareexplainedinthe

followingsections.Inaddition,asectiondedicatedtocommunicationwilldescribetheinteractionsofthevarioussubsystems.


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4 IN‐FRIDGEHARDWARE

Figure3:In‐FridgeHardwarelocationwithinthefridge

Figure3illustratesthelocationoftheIn‐FridgeHardwarewithinthefridge.Thislocationwasselectedtomaximizethereadingrangeandthustobeabletoreadanyproductlocatedinsidethefridge.TheIn‐

FridgeHardwareunitconsistsofaRFIDreader/writer,amicrocontroller,aWiFimoduleandatemperature/humiditysensor.


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Figure4:In‐FridgeHardwaresubsystemdiagram

RFIDreader/writer:Sincethereader/writerunitisanintegralpartoftheproject,therewereseveralrequirementstakenintoaccount,suchas:

• Radiowavesfrequency

• Communicationrange• DataTransferRate• PowerConsumption

• RFIDprotocolcompatibility• Price

RFIDtechnologyisusedin3mainfrequencies,LowFrequencyLF,HighFrequencyHF,andUltraHighFrequencyUHF.ItfollowsthatallotherrequirementsfortheRFIDreader/writerunitdependonthe

frequencyofthereaderasshowninTable1.Giventherequirementsoftheprojectandthesmallbudget,itwasdecidedthattheSmartFridgeprototypewouldusetheAPSX‐RW310RFIDreader/writerunit.Thisunithasarangeofapproximately25cmaboveandbelowthebuilt‐inantenna(rectangular

shape,dimensions:25cmx10cm)andapproximately8cmtothesideswithcreditcardsizeRFIDtags.TheunitcommunicatestoexternaldevicesthroughaUARTSerialport.ThefourthcolumninTable1showsthecharacteristicsoftheunit.Aswell,theprototypeSmartFridgeusestheISO15693RFID

communicationsprotocol,whichissupportedbytheAPSXreader/writerunitchosen.


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Table1:RFIDcommerciallyavailablereader/writerunitsandtheircharacteristics(Ward&vanKranenburg,2006)

LOWFREQUENCY HIGHFREQUENCY ULTRAHIGHFREQUENCY

APSX‐RW310

FrequencyRange 30‐300kHz 3‐30MHz 300MHz‐3GHz NATypicalworking

frequency125‐134kHz 13.56MHz 433MHzor

865–956MHz2.45GHz

13.56kHz

ApproximateCommunication

Range

Lessthan0.5m Upto1.5m 433MHz=upto100

metres865‐956MHz=

0.5to5metres

0.1‐0.25m

TypicalDataTransferRate

Lessthan1kbit/s Approximately25kbits/s

433–956=30kbit/s

2.45=100kbit/s

19.2kbits/s

Powerconsumption

Low Low High 20mA/5V

Characteristics Short‐range,lowdatatransfer

rate,penetrateswaterbutnot

metal.

Higherranges,reasonabledatarate,penetrateswaterbutnot

metal.

Longranges,highdatatransfer

rate,concurrentread

of<100items,cannot

penetrateswaterormetals.

Short‐range,reasonable

datatransferrate,

penetrateswaterbutnotmetal.

TypicalUse AnimalID,carimmobilizer

Smart‐Labels,contactlesstravelcards,Access&

Security

Specialistanimaltracking,Logistics

NA

Price Lowest Low High Affordable

MicrocontrollerThemicrocontrollerisinchargeofsendingcommandtotheRFIDreader/writerunit,temporarilystoreinformationofRFIDtags,preparingthemessagestobesenttothebackendserverandcommunicatingwiththeWiFimoduleandtemperature/humiditysensor.Themicrocontroller‐backendserver

communicationdetailsareprovidedinthecommunicationsectionofthisdocument.

TheArduinoUNOmicrocontrollerwasselectedfortheSmartFridgeprototypeduetoitssimplicityofuse,librariessupportandpreviousexperienceofsomeofthemembersoftheteamwiththedevice.Aswell,theArduinoUNOcomeswithreceiveandtransmitUARTserialportswhileallowingforthecreation

ofextrasoftwareserialportsifnecessary.TheArduinoUNOmicrocontrollerrequires7‐12Vand40mAcurrentperI/Opin.


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WiFiModuleInordertotransmittheinformationfromtheRFIDtagstotheserver,itisnecessarytoconnectthemicrocontrollertotheserverthroughaLANusingWiFi.WiFiwasselectedoverBluetooth,XBee,ANT

andotherwirelessprotocolssinceitisthenativelanguageoftheserver,ithasthelongestrangeanditprovidesextrafeaturesthatallowforbettercontrolandmanagementoverthecommunication.Forthisprototype,theAsyncLabsWiFishieldofferedgoodqualityatalowpricewhileprovidingbasic

transmissioncontrolprotocolsupport.ThisunitcommunicatestothemicrocontrollerthroughUARTserial.TheWiFimodulerequires250μAofcurrentand5Vtofunction.

Temperature/HumiditySensorGiventhatthemainfeatureofanyfridgesystemistheabilitytomaintainfoodproductsatalowtemperaturetoprolongtheirediblelife,theSmartFridgeprototypemonitorsthetemperatureand

humidityinsidethefridgeandreportsthevaluestotheserver.TheSHT15temperatureandhumiditysensorfromSensirioncomesalreadycalibratedandprovidesextremelyhighprecisiontemperatureandhumidityreadingswhichmakesitidealfortheSmartFridgeprototype.Thisunitisalsolowpower(30

µW/2.4‐3.6V),hasatemperaturerangeof‐40°Cto123.8°C(±0.3°Cat25°C)andrelativehumidity(RH)rangeof0‐100%RH(±2%RH).ThissensorcommunicatestoexternaldevicesthroughInter‐IC(I2C).

ISO15693RFIDProtocolTheselectedprotocolforcommunicationbetweentheRFIDtags,theRFIDreader/writerandthe

microcontrolleristheISO15693.ThisprotocolisthemostwidelyusedRFIDprotocolanditcanbefoundinmostRFIDproducts.ThisprotocolrequiresexternaldevicesattemptingtocommunicatetoRFIDtagstodosothroughbytesofdatarepresentingtherequestforinformationtothedevice.Thegeneral

formatoftheISO15693commandisthefollowing:

StartOfFile(SOF)(Nbytes)

Flags(1byte)

Command(1byte)

Parameters(0‐Nbytes)

ChecksumCRC

(2bytes)

EndOfFile(EOF)(Nbytes)

Figure5:GeneralISO15693request

WheretheflagsrepresentdifferentparametersthatdealwiththedatatransferrateandthetransmissionofthecommandtoonespecificRFIDtransponderortoalltransponderswithintheread

range,thecommandrepresentstherequestedactionandtheparametersistheinformationnecessarytoprocesstherequestedaction.

TheSOFandEOFprotocolisusuallydependantontheRFIDreader/writerunitselected.InthecaseoftheAPSX‐RW310,theSOFisequaltothenumberofbytesenclosedinthemessage(notcountingthe

SOFbyte)andtheEOFisnotspecified(thismeans,themessageisconsideredcompleteafterthechecksumbytesaresent).

MicrocontrollerRFIDreader/writerCommunicationThecommunicationbetweenthemicrocontrollerandtheRFIDreader/writerunitwasdesignedforefficiencyandeasydebugging.Numerousfunctionswereimplementedwithinthemicrocontrollercode


17

whichallowsthemicrocontrollertotransmitthenecessarybytestotheRFIDreader/writertorequestforspecificinformationfromaspecificRFIDtransponderwithinthereadingrange.

Atthemostsimplelevel,afunctionhasthetasktosendonerequestintheISO15693formattotheRFID

reader/writerunit.ThefunctionisalsoinchargeofprocessingtheresponsefromtheRFIDunitandtosavetherelevantinformationintoglobalvariablesthatcanthenbeaccessedbyotherfunctionsfordataprocessing.

Forexample,ifthemicrocontrollerneedstorequesttheRFIDreader/writerunittoreadtheUIDofall

transponderswithinthereadingrange,thenthemicrocontrollercallsasetoffunctionsthatperformsimplespecifictasks:first,themicrocontrollercallsafunctionwhichreadsoneUIDofatransponderpresentinthereadrange.TheUIDinformationisthenstoredinavariable“tagUID”.Then,thisvariable

ispassedasafunctionparametertoanotherfunctionwhichsetsthattransponderinasleepingmodeinwhichthetransponderdoesnotreactanymoretorequests.Finally,thisprocessisrepeateduntilnotranspondersreacttotherequest.

PowerThevoltageandcurrentnecessarytopowertheRFIDreader/writerunit,theWiFimodule,andthe

temperature/humiditysensorcanallbeprovidedbytheArduinoUNOmicrocontroller.Themicrocontrollerrequiresasteadypowersupplyof7‐12V.Themicrocontrollerwilldrawpowerfromthepowersupplyofthefridge.Inordertodothis,a120V‐to‐12Vregulatorwillbeplacedinparallelwiththe

powersupplyforthefridge.

Toreducetheamountofpowerconsumedbythein‐Fridgehardware,areelswitchandamagnetwillbeplacedonthefridge’sdoor.ThisswitchwillcontrolthepowertotheRFIDreader/writerunit.Theswitch

willconnecta5Voutputpintooneoftheinterruptpins,bothinthemicrocontroller.Theinterruptissettobetriggeredwhenthesignalchangesfromlowtohigh.Hence,whenthefridgedoorandtheswitchopen,theinterruptwillnotreportachange.Theinterruptwillbetriggeredwhenthedoorclosesand

thesignalgoesto5V,thussignallingthemicrocontrollerthattheitemsetwithinthefridgemighthavechanged.Themicrocontrollerwillthenreadalltheitemswithinitsrangeandreportthenewitemsettotheserver.

CasingThein‐Fridgehardwarewillbeplacedwithinaplasticcase.Thecasewillprotecttheelectronicsinsideit

fromdamagewithoutanyinterferewiththeradiowaves.Thetemperature/humiditysensorwillbeplacedontheoppositesidetothemicrocontrollerandWiFimodulestoreduceanypossibletemperatureandhumidityerrorresultingfromtheheatemanatedbytheelectronicdevices.


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5 BACKENDSERVER

TheBackendServerwasbuiltusingtheJavaProgrammingLanguage.Javawaschosenduetoits

popularity,platformindependence,andtheextensiveavailabilityoflibraries,APIsanddocumentation.Afull‐featuredprogramminglanguagewaschosenoveraserver‐sidescriptinglanguageduetothespeedofcomputationandflexibilityoftheformer.Thesystemoftenneedstodealwithlargedatasets(ie.a

fullhistoryofproductsthathavebeeninsidetheuser’sfridge),somethingthattheinterpretednatureofserver‐sidescriptingdoesnothandlewell.

ObjectHierarchyItemswithinthefridge,suchasacanofCokeoracontainerofleftoverpizza,arerepresentedwithintheBackendServerasItemTypeobjects.TheItemTypeclassisabstract–nothingcanbejustanItemType.

ThefieldsofanItemTypeobjectandtheirmeaningsarepresentedinTable2.

Table2:DescriptionofItemTypeFields

Field Descriptionid hardwareIDoftheRFIDtagattachedtothisitem

expiry_date thedateatwhichtheitemwillexpire

fridgeTimeStamps.entry_time thetimetheitementeredthefridge

fridgeTimeStamps.exit_time thetimeatwhichtheitemleftthefridge(forgood)

consumingTimeStamps alistofentrytime&exittimepairsthatdescribeeverytime

theitemwastakenoutofthefridgeandputbackin.

TherearetwoclassesthatextendItemType:LeftoverItemTypeandProductItemType.

ALeftoverItemTypeobjectrepresentsacontainerthatwasRFIDtaggedbyauser.Inadditiontoallthe

fieldsofanItemType,aLeftoverItemTypecontainsa“name”fieldthatservesasauser‐specifiedlabelofthecontentsofthecontainer.

ObjectsoftypeProductItemTyperepresentitemswithUPCcodes.ProductItemTypeobjectshaveanadditionalfieldcalled“upc”whichspecifiestheirUPC.Itisworthnotingthatthe“upc”fieldisoftype

String,despitealwayshavinganumericvalue.ThisisnecessarybecauseleadingzerosaresignificantwhenspecifyingaUPC(readbelowaboutserializationtoseewhyaxml‐primitivetypeisnecessaryinsteadofamoresophisticatedobjecttype).Forexample,twocansofCokeconstitutetwoobjectsof

typeProductItemType–bothwiththesamevalueofthe“upc”field.


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TheSmartFridgeSystemattemptstopullinformation(includingbrand,description,apicture,nutritionalinformation,etc)fromtheProductCatalogue(discussedbelow)wheneveranew

ProductItemTypeobjectisaddedtotheInFridgeSet.TheinformationpulledfromthecatalogueisidenticalforallproductswiththespecifiedUPC.Therefore,toavoidstoringmultiplecopiesofthesameinformationthisinformationisnotattachedtotheProductItemType,butisratherturnedintoanew

objectoftypeProductType.

AProductTypeisaUPCbarcodeandallofitsassociatedinformation,includingdescription,brand,pictureURL,andpotentiallynutritionalinformation.Thisobjectisintendedtocontainalltheinformationthatdoesn’tchangefromoneinstanceofaproducttoanother.Forexample,twocartonsof

milkwiththesameUPCcodecanhavedifferentexpirydates,whichiswhythisinformationiscontainedintheItemType(eachcartonwillhaveitsownItemTypeobject).However,bothcartonshavethesamebrandname,description,nutritionalinformation,andsoon.Boththe“info”(includingbrandname,

descriptionetc)andthenutritionalinformationarestoredashashtables,sincetheUPCcatalogserviceweareinterfacingwith(SimpleUPC)canreturndifferentamountsofinformationdependingontheUPCthatisqueried.

Theremainingobjectsserveascontainersforthosedescribedabove.Therearethreecontainersfor

ItemTypeobjects:

• InFridgeSet–containsallitemsthatarecurrentlyinthefridge.• HistorySet–containsallitemsthatwereonceinthefridge(ithasyettobedecidedifthisset

willonlycontainitemsforacertainperiodoftime).Onceanitemisremovedfromthe

InFridgeSet,itisaddedtotheHistorySet.Ifanitemistakenoutofthefridgeandthenputback,itleavestheHistorySetandreenterstheInFridgeSet.

ThereisalsoaProductCachethatstorestheresultsreceivedfromSimpleUPC.Inthisway,thenumberof

queriessenttotheserviceisreducedandrequestscanberespondedtomorequickly.Byseparatingthisstoreofinformation,sophisticatedcachingtechniquesbecomepossibleinordertoreduceuserwaittimeandserverbandwidth.

AFridgeSystemobjectcontainsoneofeachofthesethreesets:anInFridgeSet,HistorySetand

ProductCache.Thisisthecompletedescriptionofasystem.

AlltheobjectrelationshipsexplainedthusfararepresentedintheUMLdiagraminFigure6.


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Figure6:UMLDiagramofCoreBackendServerClasses

AddingandRemovingItemsOneofthecorefunctionsthattheBackendServermustperformistheaddingandremovingofItemTypeobjectstoandfromtheInFridgeSetandtheHistorySet.TheflowchartpresentedinFIGURE

described


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Figure7:AddingtotheInFridgeSetProcessFlow

Whenanentersthefridge,itisnecessarytodeterminewhetherthisistheitem’sfirsttimeenteringthe

fridge,orifitisbeingputbackafterhavingaportionconsumed.Ifitthesystem’sfirsttimeseeinganitemwiththisUPC(ifthereisnoentryintheProductCachewiththisUPC),itisnecessarytopullinformationfromtheProductCatalogue.IftheproductisnotavailablethroughtheProductCatalogue,

anentrywithdescription“unknown”isaddedtotheProductCache.


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NotethateventswhichtriggerHTMLgenerationarenotincludedintheaboveFigure7,asitonlypertainstoitemtracking.

TheprocessofremovingitemsfromtheInFridgeSetismuchsimplerthanaddingthem.First,theitemmusthaveitsexit_datesettothecurrenttime.Theitemisthenremovedfromthe

List<ItemType>withintheInFridgeSetandaddedtotheList<ItemType>withintheHistorySet.

SerializationItisfrequentlynecessarytotransmitcompleteobjects–thisistheroleofserialization.Arigorousmappingismadebetweenobjectfieldsandabinaryformat(inourcase,XMLtext).Inthisway,objects

utilizedbythesystemcanbewrittentofilesortransmittedeasilyandcompletely.

TheBackendServerutilizestheJava‐XMLBinding(JAXB)inordertoserializeobjects.AviablealternativetoXML‐basedserializationisJavaScriptObjectNotation(JSON).Bothformatsarepopular,withXMLbeingmoreestablishedbutJSONreceivingincreasingamountofattention.Ultimately,eitherwould

haveserverourpurposes.JAXBwaschosenduetoitsmatureandwellestablishedcodebaseandtheabilityofExtensibleStylesheetLanguageTransformation(XSLT)totransformXMLintoHTML(GlassFish,2011).ItisalsoworthmentioningthatDatabaseObjectBindingisalsoapotentialmeansofpersistent

storage,thoughitisingeneralmorecumbersome.

TheentireserializationmechanismutilizedbytheSmartFridgeSystemispresentedinFigure8.

Figure8:JavaXMLBinding(JAXB)Workflow

AnXMLschemaiswrittentospecifythefieldsofobjects.AbindingcompilerthentransformsthisXML

schemaintojavasourcefilesthatdefinethesameobjectsasdescribedwithintheschema(s).TheseobjectscanthenbeusedinanyJavacode,identicallytoanyotherobjects.ObjectsgeneratedbythismechanismcanthenbetransformedintoXMLthroughaprocesscalled“marshaling.”Forexample,the


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XML‐representationofanobjectcanbewrittentoafilethroughacalltothemarshal()function.Thesesavedobjectscanthenberetrievedbyarunningprogramthroughtheunmarshal()function,whichreceivesXMLdataasanargument.

AlloftheclassesdescribedaboveweregeneratedbyJAXBinthemannerdescribedabove,including:ItemType,ProductItemType,LeftoverItemType,ProductType,InFridgeSet,HistorySet,FridgeSystem.

TheSmartFridgeSystemreliesonXMLserializationforseveralcriticalpurposes:

• Crashrecovery• Datatransmission

• HTMLgeneration• Testing

Firstly,retrievingthestateofthesystemthroughreadingfilesprovidesamechanismforcrashrecovery.Onstartup,theSmartFridgeSystemloadsobjectsfromXMLfiles.Duringexecution,thesefilesare

periodicallywrittento,astriggeredbyaconfigurabletimer.Inthisway,minimaldataislostshouldtheserverbeterminatedforwhateverreason,andoperationisautomaticallyresumedwhenevertheserverisrelaunched.

Secondly,whenamobileclientrequestsinformation(say,thesetofallitemsinsidethefridge),the

requestedobjectsonlyneedtobemarshaledontotheOutputStreamoftheresponseobject.Further,theclientknowstheexactformoftheresponse‐theXMLschemasthatwereinitiallyusedtogeneratetheJavasourcefilesofthetransmittedobjectsspecifytheformat.

Next,XSLThastheabilitytotransformthedatapresentinanXMLdocumentintoHTML.XSLTis

essentiallyaprogramminglanguagethatisexecutedusingXMLdocumentsasinput,performingsomesortoftransformation.ForthepurposesoftheSmartFridgeSystem,wetransformtheXMLthatrepresentstheInFridgeSet(asdefinedabove)intoHTML.ThisHTMListhenmadeavailablethroughthe

webserver.

Finally,objectserializationallowsformuchsimplerandmorethoroughtesting.BecausethesystemstateisloadedfromanXMLfile,itispossibletomanuallyeditthisfileinordertocreateanydesirable

teststate.Further,aclientwascreatedinordertoaddItemTypeandProductTypeobjectstotheserver.Inthisway,theclientisabletoverifyallthefunctionalityoftheserver,includingItem/Productmanagementandnetworkfunctionality.

ForanexactdescriptionoftheXMLrepresentationofobjects,seetheXMLschemaswithinthe“FridgeSystem/schema/”folder.

Client’sResponsibilitiesNotethattheclientiscompletelyresponsibleforhowdataispresentedtotheuser,andthattheBackendServeronlytransmitsrawdata.IfweagainconsidertwocartonsofmilkwiththesameUPC

code,theusershouldlikelybeinformedthattheyhavetwocartonsofmilk.Thatis,theseitemsshould


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notbetodistinctentriesthelistofitemsthatarewithintheuser’sfridge,butratherasingleentrythatindicatestwoinstancesofthesameproduct.Furtherstill,theclientmightstillwishtoindicatethatthe

milksmighthavetodifferentexpirydates.ClearlythepresentationdecisionsoftheclientneednotdirectlyreflecttheobjectmodelthattheBackendServerrelieson.

NotealsothattheclientneedstobindthedatabetweenaProductItemTypeandaProductTypeasrequired.Forexample,iftheclienthasaparticularProductItemTypethatisinthefridgeandwouldlike

toshowitsimage,theclientmustfindtheassociatedProductType(thatis,theProductTypewiththesameUPCastheProductItemType),andlookinsidethe“info”hashtableforthevaluewithkey“imageThumbURL.”TheFridgeSystem.xmlfilecanbeusedasareferencewhendeterminingwhich

key‐valuepairsareavailableinthe“info”and“nutrition”hashtables,butnotethisinformationisn’t

necessarilyavailable(sinceitispulledfromSimpleUPC).

6 PRODUCTCATALOG

TheProductCatalogueisresponsibleforprovidingbrandnames,descriptions,pictures,andnutritionalinformation.TheBackendServerqueriestheProductCataloguebyUPC,andstorestheresulting

informationwithintheProductCache(seeObjectHierarchy).OurcurrentimplementationoftheSmartFridgeSystemutilizesSimpleUPCasaProductCatalogueservice(SimpleUPC,2010).

SimpleUPCwaschosenastheProductCatalogueforourcurrentimplementation.Theygrantedfreeaccessforthefullfour‐monthdevelopmentperiod.TheserviceprovidesanAPIforaccessingthe

followinginformationbyUPC:

• Manufacturer• Brand• Description

• SizeandWeight• Image• Ingredients

• NutritionalInformation

Further,itispossibletosearchtheSimpleUPCdatabasebykeyword.Whilethisfeaturemightbeusedtosuggestalternativestoproducts,thematchinghasabsolutelynocontextandthereforeisnotveryusefulinthisusage.Forexample,searching“yogurt”mightreturnproductssuchasyogurt‐coveredpretzels

andyogurtcoveredpretzels.Clearlythesearenotviablealternativesforaparticularbrandofyogurt.Whenimplementingthesystem,weusedthissearchfunctionalityinordertosimulateahistoryofproducts,allofwhichhavenutritionalinformation.Wewerethenabletorunouralgorithmstoensure

thattheyproducedusefulresults.

ThesystemisqueriedviaeitherXMLorJSON,andresponsesarereceivedinthesameformat.TheSmartFridgeSystemqueriesSimpleUPCthroughXML,forconsistencywithotherimplementationdecisions(namely,serialization).AnexamplerequesttoSimpleUPCispresentedinListing1,andanexample

responseispresentedinListing2.


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<request> <auth>API Key</auth> <method>FetchProductByUPC</method> <params> <upc>073731001059</upc> <params> </request>

Listing1:SimpleUPCRequestExample

<?xml version="1.0" encoding="UTF-8"?> <response> <success>true</success> <usedExternal>false</usedExternal> <result> <brand>Mission</brand> <manufacturer><![CDATA[Mission Foods]]></manufacturer> <container>Box</container> <description><![CDATA[18 Ct Taco Shells]]></description> <size><![CDATA[6.75]]></size> <category><![CDATA[Mexican Dinner Mixes, Tortillas, Corn Shells]]></category> <units>Oz</units> <upc>073731001059</upc> <ProductHasImage>true</ProductHasImage> <ProductHasNutritionFacts>true</ProductHasNutritionFacts> </result > </response >

Listing2:SimpleUPCResponseExample

ItisworthnotingthattheSmartFridgeSystemwasdesignednottorelyonaparticularProduct

Catalogue.AninterfaceexistsfromwhichaProductTypeobjectsisreceived.Inthisway,codewrittentointerfacewithanyotherservicethatprovidesthenecessaryinformationcanbeutilizedaslongasitadherestothisinterface.Further,sincethesystemonlyeverpullsinformationfromtheProductCache,

thereisalayerofabstractionbetweeninformationusedbythesystemandwheretheinformationiscomingfrom.ThisdesigndecisionissignificantsincethenutritionalfeaturesprovidedbytheSmartFridgeSystemrelyheavilyontheProductCatalogue.Shouldamorecomprehensiveorfeature‐rich

cataloguebeavailable,theSmartFridgeSystemneedsonlytobeadjustedslightlyinordertoleveragethesuperiorcatalogue.

7 COMMUNICATION

SeveralcomponentsoftheSmartFridgeSystemexchangeinformation.Eachofthesecommunication

exchangesispresentedinFigure9andexpandedinthefollowingsubsections.


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Figure9:CommunicationOverview

AsobserverinFigure9,allinter‐componentcommunicationgoesthroughtheBackendServer.TheservicesprovidedbytheBackendServerarethereforefirstdiscussed,andthenhowthevariouscomponentsutilizetheseservicesisexpandeduponinsubsequentsections.

ItisimportanttonotethattheHypertextTransferProtocol(HTTP)playstwodistinctroleswithinthe

SmartFridgeSystem:astandardrolewhenwebclientssendrequeststothewebservertofetchHTMLfiles,andacustompurposewhentheIn‐FridgeHardwareormobileappsendandrequestinformationtoandfromtheserver.OurcustomusageoftheHTTPprotocolisspecifiedinthefollowingsubsections.

ForthedefinitionofHTTP,see(Fielding,Gettys,&Mogul,1999).

BackendServicesAllcommunicationtotheBackendServerisfacilitatedbyHTTP.ClientssendrequeststodifferentUniversalResourceIdentifiers(URIs)inordertoperformdifferenttasks.ForHTTP,URIshavethefollowingformat:

http://<server_ip>:<server_port>/<path>?<query>

HTTPwaschosenasamessageformatformanyreasons.Firstly,testingisfacilitatedtheabilitytouseanybrowserasaclient.Further,HTTPisaveryestablishedprotocolforwhichtherearelibrariesonessentiallyallmodernplatforms.Anarbitrarymessageformatcouldhaveeasilybeendecidedon,but

theubiquityofHTTPlibraries(andasaprotocolingeneral)leftlittlereasonforacustom‐designedprotocol.

ForthepurposesoftheBackendServer,the<path>portionoftheURIcanhaveoneofthevalues

describedinTable3(notethatthesevaluesarecasesensitive).

Table3:PathsMadeAvailablebyServer

Path DescriptionSHOW RetrievesinformationfromtheserverinXMLformatasdefinedin

FridgeServer/schema.ThequeryportionoftheURI(discussedbelow)specifieswhatinformationisreturned,butmostcommonlyitwillbethecurrent

In‐FridgeHardware

HTTP:/ADD_ITEMSBackendServer

MobileClient(iPhoneApp)

HTTP:

/SHOW/ADD_OBJECT

WebServer

WebClient(Browser)

PHP

HTTP(standardfetch)

HTTP:

/GENERATE_HTML/PLOT_DATA


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contentsofthefridge.Nocontentisnecessarywithintherequestbody.

SAVE Allowsclientstocausetheservertosaveitscurrentstate.Afilenamecanoptionallybeincludedwithintherequestbody,otherwiseadefaultfilenameisused.

ADD_OBJECT Allowsclientstoaddfully‐formedXMLobjectstotheserver,andisthereforeusedprimarilyfortesting.CurrentlysupportedobjectsincludeItemTypesandProductTypes.TheobjecttobeaddedmustappearwithintheHTTPrequestbodyintheXMLformatspecifiedinFridgeServer/schema.ThequeryportionoftheURIallowsuserstospecifywhichsetobjectswillbeaddedto,asdiscussedbelow.

ADD_ITEMS The“real”pathusedbytheIn‐FridgeHardwareunit.TheHTTPmessagebodyincludesXMLthatdefinesthesetofallitemscurrentlyinthefridge.Theserverthencomparesthisincomingsettothe“current”setinordertodeterminewhichitemshavebeenremovedandadded.

GENERATE_HTML UsedtogeneratetheHTMLrepresentationofinformationthatismadeaccessiblethroughthewebserver.ThisHTMLisgeneratedthroughXSLTransformations.TheexactHTMLthatcanbegeneratedispresentedinTable4.

PLOT_DATA Providesasetofpointswithintheresponsebody,havingtheformat:“[[0,0],[1,1],…]”.Thedataavailablethroughthispathisusedbythewebserverandmobileapptopresentgraphicalinformation.TheexactinformationthatisavailableispresentedinTable4.

IfarequestwithapathotherthanthosespecifiedinTable3isreceived,theserversendsaHTTPResponseHeaderwithcode404(NotFound).IfanentrydoesnothavearesponsespecifiedinTable3,

theserverwillrespondwithonlyaResponseHeaderwithcode200(indicateeverythingisOK).

The<query>portionoftheURIcontainsasetofkey‐valuepartsseparatedby‘&’symbols.For

example,avalidrequesttotheBackendServerwoulduseaURIsuchas:

http://127.1.1.8:8278/SHOW?target=SYSTEM

TheresponsebodywillthenhavealltheinformationaboutthecurrentFridge‐SysteminXMLformat(includingInFridgeSet,HistorySetandProductCache).However,clientswilltypicallynotneedadescriptionoftheentirefridgesystem,butratherjusttheInFridgeSet.Completedescriptionsofthekey‐

valuepairsthatarerequireorpossibleforeachURIpathispresentedinTable4.

Table4:PathsandtheirQueries

Path Query Description

SHOW

target={SYSTEM|INFRIDGE|HISTORY}

Optional.Specifieswhichsetisreturnedinthebodyoftheresponse.

SAVE None


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ADD_OBJECT target={INFRIDGE|HISTORY}casesensitive

MandatoryifItemTypeisbeingadded,unnecessaryforProductTypes.Specifieswhichsettheobjecttobeaddedshouldgointo.

ADD_ITEMS None GENERATE_HTML target={INFRIDGE|

HISTORY|TIME_SENSITIVE}

Mandatory.SpecifieswhatHTMLwillbegenerated.IfINFRIDGEorHISTORYissupplied,theHTMLrepresentationofthatsetisgeneratedintothestandardHTML(web/html)folder.IfthevalueisettoTIME_SENSITIVE,theHTMLthatrepresentstheexpiringsoon,alreadyexpiredandrecentlyremoveditemsareallgenerated.

PLOT_DATA target={EXPIRY_HISTORY|<upc_value>}

Mandatory.SupplyingtheEXPIRY_HISTORYtargetreturnsx‐valuesrepresentingmonthsandy‐valuesrepresentingthenumberofitemswhichexpiredbeforebeingremovedforthatmonth.IfthetargetsuppliedisaUPCnumber,thex‐valuescorrespondtomonthsandthey‐valuesindicatehowmanytimestheproductwaspurchasedinthatmonth.

Important:AllrequestsmadetotheBackendServermustusetheGETmethodofHTTP.

Shouldamalformedquerybereceivedbytheserver,aresponsecodeof400(BadRequest)willbesentandtherequestwillbeignored.

InFridgeHardwaretoBackendServerCommunicationAsmentionedbrieflyabove,theIn‐FridgeHardwareunitreliesonHTTPtocommunicatetotheBackendServer.Thein‐FridgehardwaresendstwodifferentHTTPmessagestypestothebackendserver.Thefirst

messageissentevery60secanditcontainsthetemperatureandhumidityreadingsfromthetemperature/humiditysensorinaXMLformat.

Toindicatethecurrenttemperatureandhumidityoftheinsideofthefridge,theIn‐FridgeHardwareunitwouldsendarequesttoaURIoftheform:

http://<server_ip>:<port>/TEMP_HUM

TheHTTPrequestbodythencontainsXMLthatdefinesthecurrenttemperatureandhumidityinsidethefridge.AnexampleofthisXMLisdefinedinListing3.

<temperature>10.1254</temperature>

<humidity>78.9034</humidity>

Listing3:ExampleofXMLSentfromIn‐FridgeHardwaretoBackendServer


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InthesecondmessagetypeTheIn‐FridgeHardwareunitsendsanXMLrepresentationofalloftheitemscurrentlyinthefridge.ItisthentheBackendServer’sresponsibilitytodeterminewhichitemswereremovedoraddedtothefridge.

Toindicatetheitemscurrentlyinthefridge,theIn‐FridgeHardwareunitwouldsendarequesttoaURI

oftheform:

http://<server_ip>:<port>/ADD_ITEMS

TheHTTPrequestbodythencontainsXMLthatdefinesthesetofitemscurrentlyinsideofthefridge.AnexampleofthisXMLisdefinedinListing4.

<itemset>

<item>

<id>0000110101</id>

<upc>20202020202</upc> <expiry_date>20-08-2011<expiry_date>

</item>

<item> <id>00222222</id>

<upc>333030303</upc>

<expiry_date>20-08-2011<expiry_date>

</item> </itemset>

Listing4:ExampleofXMLSentfromIn‐FridgeHardwaretoBackendServer

TheIn‐FridgeHardwaredoesnotexpectanyresponsefromtheserverbeyondthestandardHTTP

ResponseHeaderwithcode200(indicatingeverythingisok).ShouldtheIn‐FridgehardwaresendmalformedXML,theserverwillresponsewitha400errorcode(BadRequest).

MobileApptoBackendServerCommunicationInordertopresenttheitemscurrentlyinthefridge,theiPhoneapplicationmustreceivethisinformationfromtheBackendServer.ThisinformationisretrievedbyanHTTPrequestwiththe

followingURI:

http://<server_ip>:<port>/SHOW?target=INFRIDGE

TheHTTPResponseBodythencontainstheXMLdefinitionoftheInFridgeItemSet(asdefinedinthe

ObjectHierarchySectionabove).ForafulldefinitionoftheXMLformatofobjects,seetheschemaswithinthe“FridgeSystem/schema/”folder.AfterreceivingtheXMLrepresentationofthecurrent

fridgecontents,theapplicationparsesthisdataandpresentsittotheuserinanaccessibleformat.

TheiPhoneapplicationalsosendsinformationtotheBackendServerwhenauserhasmanuallytaggedanitemwithaUPCoraleftovercontainer.Ineithercase,theiPhoneapplicationsendstheinformationwithintherequestbodyofanHTTPmessagetoaURIsuchas:


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http://<server_ip>:<port>/ADD_OBJECT

Inthecaseofamanually‐taggeditemwithaUPC,therequestbodycontainsthevalueoftheUPCcode.

Ifaleftoveritemwasadded,thelabelsuppliedbytheuserissentintherequestbody.TheservertheninterpretsthenextitementeringthefridgewithoutaUPCcodeashavingthevalue(UPCorname)asreceivedfromtheiPhoneapplication.IfthemessagebodydoesnotspecifyalabeloraUPC,therequest

isignoredbytheserver.

WebServertoBackendServerCommunicationAstandardwebserver(suchasApache)isutilizedinordertoprovidetheweb‐accessiblecontentoftheSmartFridgeSystem.TheservermusthavePHPinstalledinorderforthewebcontenttobepresented.Further,theWebServerandtheBackedServermustresideonthesamephysicalmachine:theBackend

ServerproducesHTMLfilesthatmustresidewithintheWebServer’srootwebdirectory(asspecifiedbytheDocumentRootpropertyinApache).Inthisway,theWebServermakesthefilesgeneratedbythe

BackendServerwebaccessible.

HTMLAssemblyThePHPrunningthroughthewebservercollectsandpresentstheHTMLgeneratedbytheBackendServer.TheBackendservergeneratedper‐UPCHTMLfragmentsthatareamalgamatedintoasinglewebpagebyaPHPscript.Forexample,thefile“web/html/inFridge/011161133971.html”containsontheHTMLtorepresentallitemswiththeUPCof011161133971.Allofthefileswithinthe“web/html/inFridge/”directoryareassembledintoasingleHTMLfile,whichthenrepresentsallUPCscurrentlyinthefridge.Inthisway,wheneveritemsareaddedtoorremovedfromthefridge,only

HTMLfragmentsneedtobegenerated–avoidingredundantgenerationoftheHTMLrepresentationsofallthefilesthatdidnotchange.ThoughthismechanismaddscomplexitytothePHPrunningonthewebserver,itsignificantlyreducestheamountofXSLTprocessingrequiredontheBackendServer.

TimeDependentContentItissometimesnecessarytoregeneratecertainHTMLfiles.Forexample,thetablethatpresentswhich

itemsareexpirysoonorthepagepresentingitemsthatwereremovedrecentlymustberegeneratedinorderforthetransientnotionof“soon”toremainvalid.InordertotriggerthisHTMLgeneration,thewebserverusesaPHPscriptthatsendsanHTTPrequesttoaURIsuchas:

http://<server_ip>:<port>/GENERATE_HTML?target=TIME_SENSITIVE

Thisrequestissenteverytimeauseropensanyofthefollowingwebpages:

• InFridge.php• Expiry.php• RecentlyRemoved.php

Itisthereforeensuredthatalltime‐sensitivedatapresentonthewebsiteisuptodate.


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PlottingThewebserveralsopresentsplotstotheuser.Theplotmayshowhowmanyitemswereexpiredbeforebeingremovedfromthefridge(indicatingpotentialwaste)orhowoftenaparticularproductwaspurchasedwithinthepastyear.ThoughtheplotisultimatelypresentedusingJavaScriptandCSS

libraries,thedatapresentedontheplotmustbefetchedfromtheBackendServer.

DataisreceivedwithinthemessagebodyofaresponsetoaURIsuchas:

http://<server_ip>:<port>/PLOT_DATA?target=EXPIRY_HISTORY

Thex‐valuesofthedatarepresentmonthsandthey‐valuerepresentsthenumberofitemsthatwere

expiredwhentheywereremovedfromthefridgeofthatmonth.ThesepointsarethenpassedintoaPHPscriptthatplotsthedataonagraphusingFlotrlibraries(Solutaire,2011).

8 SOFTWARESYSTEM

AutoGeneratedGroceryListTheauto‐generatedgrocerylistfeatureusesanintelligentalgorithmthatmonitorsnumerous

parametersinordertoautomaticallyselectthemostappropriateitemstobeplacedonagrocerylistfortheuser.Recordingofusagepatternsgivesthealgorithmthenecessaryinformationtomakeinformed

decisionsaboutwhichitemsshouldbeaddedtothegrocerylist.Thedynamicnatureofauser’sgroceryisaproblemwehaveconsideredinthedesignofthisalgorithm.Forexample,ausermaybuyanitemoneortwoweeksinarowthenloseinterestnolongerhavingadesireforthatitem.Toachieveaccurate

resultswemusthavesomemeasureofdesirabilityforeachitem.Thecentralassumptionthathasbeenmadeisthatanitemwhichhasnotbeenpurchasedinalongtimeisassociatedwithlowdesirabilityandshouldnotbeplacedonthegrocerylist.Thealgorithmdesignincorporatesatypeoflearningthatyields

moreaccurateresultsthelongeryouusethesmartfridgesystem.Thealgorithmcomponentswillnowbediscussedindetail.

AlgorithmInterfaceThealgorithmrequiresanumberofinputparametersinordertogainanunderstandingoftheusagepatternsinadditiontothecurrentstateoftheuser’sfridge.Aseriesofitemlistsareusedforthispurpose.TheSmartFridgeSystemkeepsarecordofwhatitemsarecurrentlyinsidethefridgeatany

giventime.Thiscurrentitemlistreflectsthepresenttimestateofthefridgecontents.Inadditiontothecurrentstateofthefridgeweneedinformationaboutthehistoryofitemspassinginandoutofthefridge.Thisinformationisgainedthroughthehistoryitemlistwhichnotonlykeepstrackofwhatitems

passedintoandoutofthefridgebutalsothetimesinwhichtheseeventsoccurred.Thethirdandlastparameternecessaryismasteritemlist.ThemasteritemlistcontainsasingleinstanceofeveryitemwhichhasevenbeenrecognizedbytheSmartFridgeSystem.Thepurposeofthislististoserveasa

referenceofallknownitemsirrespectiveofbeinginthefridgecurrentlyorinthepast.Themasteritemlistisalsousedtokeeptrackofuserspecifiedparametersonanitemperitembasis.Tosummarize


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threeinputparametersareused,thecurrentitemlist,thehistoryitemlistandthemasteritemlist.Uponcompletionofthealgorithmanitemlistisproducedcontainingthegrocerylistitems.

Component1Certainitemscanbespecifiedbytheusertoalwaysbeontheirgrocerylist.Irrespectiveofallotherfactorsanitemflaggedas“alwayson”willalwaysappearonthegrocerylistifthatitemisnotcurrently

insidethefridge.Itemslabelledas“alwayson”arespecifiedinthemasteritemlistbytheuser.Thealgorithmsearchesthemasterlistforthe“alwayson”flagset,thencomparesthisitemwiththecurrentitemlist.Iftheitemisnotfoundinthecurrentitemlistitwillimmediatelybeaddedtothegrocerylist.

Component2Thiscomponentattemptstopredicthowdesirableaparticularitemisbaseduponthetimesinceitwas

lastpurchased.Thegeneralassumptionisitemswhichhavenotbeenpurchasedrecentlyarenotlikelytobeofinteresttotheuseranylongerandshouldnotbeplacedonthegrocerylist.Thecomponentfunctionsinthefollowingway.First,alistisgeneratedthatrepresentsitemswhichhavehighbuying

potential.Thislistisobtainedbysubtractingtheitemsappearinginthecurrentitemlistformthehistoryitemlist.Forthepurposedofthiscomponentweassumetheuserwouldn’twantanyitemsthatarestillinsidetheirfridge.Thegeneratedlististhensearched.Eachiteminthelisthasanattributecontaining

thepermanentexittimefromthefridge(i.e.timeofbeingentirelyconsumed).Theexittimestampiscomparedagainstapre‐determinedthresholdvalue.Ifthedifferencebetweenthepresenttimeandexittimeisbelowapredeterminedthresholdthentheitemisaddedtothegrocerylist.Ifthedifferenceis

greaterthanthethresholdthenweassumetheuserisnolongerinterestedinthisitemanditisnotadded.Achallengingfactorwastodetermineasuitablethresholdperiod.Toolongofaperiodwouldmeanthattoomanyitemsareaddedtothelist,manyofwhichmaynotbeofinteresttotheuserany

longer.Ontheotherhandtooshortofperiodwouldresultinitemsofinterestnotbeingadded.Specialconsiderationwasgiventofindthemostappropriatecompromise.Thethresholdwasdecidedtobe14day.Thisdecisionwasbasedonanaverageshoppingperiodofonceaweek.Iftheuserdidnotpurchase

theitemwithintwogrocerytripsweassumedtheywerenolongerinterestedinpurchasingthisitem.

Component3Oneofthemorechallenginginsightstohaveregardingthecontentsofyourfridgeistheapproachingexpirationdates.TheSmartFridgeSystemisabletomonitoreachitemsexpirationdateandusethisinformationtoinitiateapre‐emptivepurchase.Basedonouroriginalassumptionwecanassumethat

itemswhicharecurrentlyinthefridgeareofhighinteresttotheuser.Thealgorithmsearchesthroughthecurrentitemlistcomparingeachexpirationdatetothepresentdate.Ifthedifferencebetweenthecurrentdateandexpirationdateisbelowapre‐determinedthresholdtheitemisaddedtothegrocery

list.Againthechallengeoffindasuitablethresholdvalueisseen.Thethresholdforthiscomponentwassetat7days.Thedecisionwasbaseduponanaveragegroceryshoppingscheduleofonceperweek.Witha7daythresholdtheitemisensuredtobepurchasedonthelastgroceryshoppriortoexpiration.

Ideallywewouldliketheitemtobeaddedonlyonthelastgroceryshopbeforeexpiring.Ifthethresholdweresettoohighthenthepre‐emptivepurchasewouldoccurtoosoon.Theresultcouldbewastingof


33

foodastheexpirationdateofthepre‐emptivelyboughtitemwouldbeearlierthanifwehadwaiteduntilthelastmoment.

Component4Thefourthcomponentisusedtopredictwhenanitemisnearingtheendofitscontents.Thisportionofthealgorithmisadaptiveandlearns,theSmartFridgeSystemyieldseverimprovingresultsastime

progresses.TheSmartFridgeSystemassignstoeachitemanentrytimeandanexittime.Theentrytimeisthetimeforwhichtheitemwasfirstplacedinthefridgewhiletheexittimeiswhentheitemwaspermanentlyremovedfromthefridge.Bytakingthedifferencebetweenexitandentrytimeswecan

gaininsighttotheconsumptiontimeofthisitem.Astheusergoesthroughrepeatedcyclesofbuyingaparticularitemandconsumingit,wecanaverageoveralltheseindividualconsumptiontimes.Asthe

numberofcyclesincrease,theaverageconsumptiontimebecomesabetterestimateoftheactuallyconsumptiontime.Inadditiontotheaverageconsumptiontime,acurrentconsumptiontimemustbecalculated.Foreveryiteminthefridge,acurrentconsumptiontimeiscalculatedbytakingthe

differencebetweenpresenttimeandentrytime.Thisnumberrepresentstheamountoftimetheuserhasbeenconsumingtheitem.Tocompletethedecisionofwhetherornottoaddtheitemagainathresholdfactorisneeded.Thethresholdvalueforthiscomponentisapercentageoftotal

consumption.Forexample,wemighthavecalculatedthecurrentconsumptiontimeis90%oftheaveragetotalconsumptiontimeforthisitem.Wewouldthenchoosetoaddtheitembecausethereisagoodchancethatitisnearlyentirelyconsumed.Aswithpriorthresholdvaluesacompromiseisseen.If

thethresholdissettoolowthenitemswouldbeaddedtothegrocerylisttooearlyandmightresultinwastingoffood.Similartothepriorsituationwithexpirationdates.Theusermaynotbeabletoconsumetherestofthepreviousitemandthenewitembeforethenewitemsexpirationdate.Onthe

otherhandifthethresholdissettoohighthentheitemmaybeconsumedbeforetheuserhasareasonablechancetopurchasetheitemduringtheirnexttriptothegrocerystore.Thedecisionwasmadetosetthisthresholdto90%.

Component5Thefinalcomponentofthealgorithmallowsanotheruserspecifiedvaluetocontrolwhatisaddedtothegrocerylist.Someusersmaywanttheoptiontospecifyaquantityofanitemtheywouldalwayslike

tohaveinthefridge.Forexample,theusermaysayIwouldliketohave3bottlesofapplejuiceinthefridgeatalltimes.Thealgorithmwillsearchthecurrentitemlistandmakesurethisrequirementissatisfied.Ifthequantityofanitemislessthantheuserspecifiedquantitythenitgetsaddedtothe

grocerylist.Thedifferencebetweentheuserspecifiedquantityandthecurrentquantityisthevalueaddedtothegrocerylist.Iftheitemcannotbefoundinthecurrentitemlistitthenitgetsaddedtothegrocerylistwiththeuserspecifiedquantity.

SummaryThesmartfridgeauto‐generatedgrocerylistfeatureusesanintelligentmultivariablealgorithm

illustratedbelow.Anumberofimportantfactorsareconsideredusingrecordedusagepatternsinadditiontouserspecifiedinformation.Wehavefocusedourattentiontofivemaincomponentswebelievetoyieldthemostaccurategrocerylistpossible.Thefirstcomponentgivestheusercontrolto


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makesureaparticularitemisneverforgottenirrespectiveofanyotherfactors.Thesecondcomponentpredictsthedesirabilityofanitembasedonhistoryusagepatterns.Thethirdcomponentpre‐emptively

identifiesitemswhichhaveexpirationdatesinthenearfuture.Thefourthcomponentidentifiesitemswhichhaveahighprobabilityofbeingconsumedentirelyinthenearfuture.Thefifthandfinalcomponentallowstheusertoensureaspecifiedquantityofanitemisalwaysavailableinthefridge.The

culminationofallfivecomponentsgivesacomprehensiveimageofwhatitemstheuserismostlikelytohaveontheirgrocerylistiftheyweretomanuallywriteitthemselves.


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Figure10:Auto‐generatedGroceryListAlgorithm


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NutritionMetricSystemIdentifyingthenutritionalvalueofafooditemisadifficulttaskformostofthepopulation.TheSmartFridgeSystemincorporatesanutritionalmetricssystemusedtopresentnutritionalinformationina

concise,easytounderstandformat.Thenutritionalvalueofanitemischallengingtopresentbecausenutritionalvalueisrepresentedbynumerousparameters.Forexample,theamountoffat,cholesterol,carbohydrates,protein,vitaminsetc.allmustbeconsideredtogainperspectiveabouthownutritiousan

itemis.TheSmartFridgeSystemusesamathematicalmodeltoreducethismultivariableproblemtoasinglenumberthatrepresentsthenutritionalvalue.Themodelisdescribedbelow.

NutritionalProfilingModelThemodelweusedintheSmartFridgeSystemwasbaseduponaconceptcallednutritionalprofiling.Theideaistoconsiderthemaincomponentsofafood,namelyfats,protein,carbohydratesetc.and

quantifytheentirenutritionalvaluewithasinglenumber.Wechosetouseamodeldiscussedinapapercalled“ModelingExpertOpinionsonfoodHealthiness:ANutritionalMetric.”InthispapertheysurveyedtheleadingU.Snutritionexpertsaboutthehealthinessofsamplefoodandbeverageproducts.Each

expertwasgivenanumberofsamplefoodstogetherwithcorrespondingnutritionalinformation.Aftergiventimetoanalyzethesample,theexpertwasrequestedtoprovideascorebetween‐5to5.‐5representedextremelyunhealthywhile5representedextremelyhealth.Afteralltheexpertshadmade

judgementsonalltheitemsalinearregressionwasuseddevelopanequationfortheresults.Theequationconsidersthe12parametersprovidedbyastandardnutritionalfactslabel.Usingthismodelwewereabletoquantifythenutritionalvalueofasingleitem.

SystemDescriptionThenutritionmetricsystemreliesontwoclassesforitsfunctionality.TheNutritionItemclassisusedtorepresentthenutritionaldataofanitemwhiletheNutritionMetricsclassoperatesontheNutrition

Itemobject.Thetwoclassesaredescribedinfurtherdetailbelow.

NutritionItemClassThenutritionitemisaclassusedtorepresentthenutritionallyrelevantinformationaboutaparticularitem.Attributesincludeallinformationpresentonastandardnutritionalfactslabelinunitsofpercentdailyvalue.Thenutritionprofilingmodelisimplementedinthisclassasamethod.Afewothermethods

werenecessarytoconvertpercentdailyvaluestounitsofgrams.Theunitconversionwasnecessaryfortheuseofournutritionalprofilingmodel.

NutritionMetricsClassThenutritionmetricsclassiscomposedofanumberoffunctionsthatusethenutritionitemclasstoprovidethecorefunctionalityofthesystem.

ConstructNutritionItemTheitemlistsusedtorecordthecurrentandhistoryoftheSmartFridgeSystemdiscussedintheprevioussectiondonostorenutritionalinformationaboutthoseitems.Thisdecisionwasmadeto

conservespacebypreventingtheduplicatestorageofnutritionaldataabouteachitem.TheProductCachelistisusedtostoreasingleinstanceofanitemtogetherwithitsnutritionalinformation


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storedinsideahashtable.Nutritionalinformationisrecalledfromthishashtableusingkeyvaluepairs.Thekeyisthenameofthenutrientwhilethevalueisthepercentdailyvalueofthatnutrient.The

getNurtritionItemfunctionprovidestheconstructionofanutritionitemobjectgivenanitemfromthecurrentitemorhistoryitemlists.Thefunctionidentifiestheitemintheproductcacheandgetsnutrientinformationviathehashtable.Thenutrientitemisthenreturnfromthefunction.

TopFiveListsThetopfivelistsfunctionisusedtoidentifythe5mostand5leastnutritiousitemsinalist.Itusesasingleinputparameter,alistofitems.Thiscouldbeusedforthecurrentitemlisttoconstructatopfive

listofitemscurrentlyinsidethefridge.Inaddition,itcouldbeusedonthehistoryitemlisttoseethemosthealthyandleasthealthyitemseverconsumed.Thefunctionoperatesbycalculatinganutritional

valueforeachitemintheinputlistandstoringthevalueinanarray.Thearrayisthensearchedforamaximumandminimumnutritionalvalue,recodingtheindexinthearray.Theitemwiththisindexisthenaddedtothetopfivelistarray.Theitemjustaddedarethenremovedandtheprocessisrepeated

tofindthenextmaximumandminimumvalues.Thisprocessiscarriedonuntilthetop5mostandleastnutritiousitemsareidentifiedandstoredintheoutputarray.

AverageNutritionalValueofListThisfunctionisusedtocalculatetheaveragenutritionalvalueofanentireitemlist.Thefunctiontakesasingleinputparameter,anitemlist,andreturnstheaveragenutritionalvalueofthelist.Thecalculationisaccomplishedinthefollowingway.Foreveryiteminthelistconstructanutritionitemobject.Next,

callthemethodtocalculatethenutritionalvalueforeachonthenewlycreatednutritionitemobjects.Takethesumofallnutritionalvaluesanddividedbythenumberofitemsinthelisttogettheaveragenutritionalvalue.Theaveragevalueisthenreturned.

ItemsinRangeThisfunctionwasnecessaryasahelpertoaccomplishothercalculationsinthesystem.Theinput

parametersarealistofitemsandtwodates.Thetwodatesrepresentastartdateandanenddate.Thefunctionsearchesthroughtheitemlistforitemswhichhaveanexitfridgetimethatoccursinbetweenthestartandenddates.Thefunctionreturnsalistofitemsthathaveexittimesthatfallwithinthe

specifiedtimespan.Sincetheexittimerepresentsthetimeinwhichanitempermanentlyleftthefridgethisfunctioncanbeusedtoidentifywhatitemswereentirelyconsumedwithinatimespan.

NutritionalValueversusTimeThefinalfunctionisusedtogenerateaplotofnutritionvalueofconsumeditemsovertime.Theinputparametersarealistofitems,normallythehistorylist,andanintegerrepresentingthenumberofweeksintothepasttobeanalyzed.Theoutputisgivenanarray,eachindexstorestheaverage

consumeditemnutritionalvalueforasingleweek.Wedecidedtouseasingleweekresolution,becausethisensuresahighprobabilityofatleastafewitemsbeingconsumedwithinthattimeperiod.Iftheresolutionwastobeasingledaythendayswherenofoodwasconsumedwouldhaveanaverage

nutritionalvalueofzero.Thecalculationisaccomplishedinthefollowingway.Thespecifiedtimeperiodisbrokenupintosingleweeksintothepast.Foreachweek,asearchisperformedtoidentifyallitemswhichwereconsumedwithinthatweek.The“itemsinrange”functiondescribedabovewasusedfor


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thistask.Oncealistofitemsconsumedfortheweekwasconstructedwecalculatedtheaveragenutritionalvalueofthatlist.Anormalizationfactorwasusedtoaccountforhowlongittooktoconsume

anitem.Forexample,anunhealthyitemmayhavebeenconsumedonlyveryslowlyandshouldthereforeholdlessweightintheaveragingcalculation.Incontrastanitemconsumedveryquicklyshouldholdahigherweightintheaveragingcalculation.Oncetheaveragenutritionalvalueiscalculated

itgetsaddedtotheoutputarray.Theprocessiscompletedforeveryweekspecifiedbytheinputparameterweekvalue.Uponcompletionthearrayisreturned.Eacharrayindexholdstheaveragenutritionalvalueforallitemsconsumedinthatgivenweek.

Figure11:NutritionalMetricsSystemStructure

9 MOBILEAPPLICATION

OverviewThemobileappwasdesignedusingtheObjectiveCprogramminglanguagetorunexclusivelyonthe

iPhone3GSandtheiPhone4.Thepurposeofthemobileappistoprovideaclear,useful,easytouseuserinterfacefortheusertoaccessinformationfromtheirRFIDSmartFridge.Thefivemaincomponentsofthemobileappare“InmyFridge,”“Expiring,”“GroceryList,”“EatHealthy,”and“Scan

Barcode”asdenotedbythefiveiconsalongthebottomofthescreeninthefigurebelow.Theusercanswitchbetweenthesedisplayseasilybysimplyclickingortappingthescreenoverthedesiredicon.“InmyFridge”displaysaninventoryoftheitemscurrentlyinthefridgeorganizedbycategory,asseenin

thefigurebelow.Whentheuserclickson“Expiring”asimilardisplayshowingalltheitemscurrentlyinthefridgeandtheirexpirydate,organizedfromtheitemswhichwillexpiresoonesttolatest.Clickingthegrocerylistwilldisplayagrocerylistpredictedfortheindividualuserbasedontheirconsumption


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history(seetheAuto‐GeneratedGroceryListSectionunderSoftwareSystem).The“EatHealthy”displaywilldisplaythefridge’scurrenttemperatureandhumidityatthetopofthescreen.Thiswillbe

followedbyalistofthetopfivemostnutritiousandtopfiveleastnutritiousitemsinthefridge(seeTopFiveListssectionunderNutritionMetrics).Fromtheretheusercanscrolldowntoseeagraphoftheaveragehealthinessofalltheitemsconsumedfromtheirfridgeversustime(seeNutritionalValue

versusTimesectionunderNutritionMetrics).Finally,the“ScanBarcode”displaywillshowabuttoncalledScan.OnceScanisclickedtheappwillbringupthecameraandamessagewhichaskstheuserto“adjustthecamerasothebarcodeoftheitemtobeaddedisinviewthentapthescreen”.Oncethe

usertapsandthebarcodeisverifiedamessageto“pleaseadditemwithreusableRFIDtagtofridge”aswellasacancelbuttonwillbedisplayeduntiltheuseraddstheitemtothefridgeofclickscancel.

Figure12:MobileApp‐InMyFridgeDisplayScreen


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MobileAppSystemDesign

TheapplicationisinitializedatthetopbytheAppDelegateclasswhichinstantiatestheobjecttabBarControlleroftypeUITabBarController.ThisobjectcontrolsthetabbarseenatthebottomofthescreeninFigure12(above),aswellaseachview(alsoobjects)associatedwiththetabs.The

AppDelegatethenproceedstoinstantiatefiveviewobjectsfromeachoftheclassesInFridgeView,ExpireView,ShoppingListView,EatHealthyView,andBarCodeController.TheAppDelegatethenassociatestheseviewstabBarController,suchthatthesefiveclassesrespectivelycontroltheviewsof

eachofthefivetabsseenatthebottomofFigure12fromlefttoright.

ThefourviewcontrollerobjectscreatedfromtheclassesInFridgeView,ExpireView,ShoppingListView,andEatHealthyVieweachdisplaydifferentdata(describeintheOverviewsectionabove)drawnfromthebackendserver.Theyeachcreateanobject,connectToServer,usingtheclassConnectToServer

which,whenthatparticularviewisbeingdisplayed,sendsarequest(seeMobileApptoBackendServerCommunicationsection)everythirtysecondscheckingforupdateddata.Thebackendserverthenreturnsanxmlfilecontainingtherequestedlistofitems.Forinstancethe“InMyFridge”viewwould

sendarequesttotheserverandwouldreceiveanxmlfilecontaininginformationoneachoftheitemscurrentlyinthefridge.ThesexmlfilesarethenparsedbyeachviewcontrollerobjectusingtheclassXMLParseandthedataforeachitemisstoredinobjectscreatedfromtheclassFridgeItem.Theview

controllerobjectsthendisplaythisdatainatablecreatedfromtheclassUITableView.Eachofthefourviewcontrollerobjectscustomizestheirtable.

InFridgeViewcustomizesthetableitdisplaystoshoweachitemcurrentlyinthefridgeandhowlongithasbeeninthefridge,aswellasitemsthathavebeenrecentlyremovedfromthefridge(withinthepast

twentyminutes)andhowlongagotheywereremoved.TheseitemsarearrangedaccordingtocategoryasdescribedintheirUPCcode.ExpireViewshowseachiteminthefridgeandtheirexpirydates

arrangedfromtheitemthatwillexpireintheshortestperiodtotheitemthatwillexpireinthelongest

Figure13:MobileAppClassHierarchy


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periodoftime.ShoppingListViewwilldisplayanauto‐generatedgrocerylist(seetheAuto‐GeneratedGroceryListsectionunderSoftwareSystem).FinallyEatHealthyViewwillhaveatablecontainingthetop

fivehealthiestandleasthealthyfoodsaswellasthefridge’scurrenttemperature,humidity,andagraphoftheaveragehealthinessoftheitemsinthefridgevstime.ThisgraphwillbegeneratedwithintheEatHealthyViewclass.

TheBarCodeControllerclasscreatestheviewdescribeintheOverviewsection(above)wheretheuser

pressesthe“scan”buttontoscanabarcodeofanitemwithoutanRFIDtagusingtheiPhone’scamera.TheBarCodeControllerclassthenusestheZBarSDKlibrarytoanalyzetheimageofthebarcodeanddetermineitsassociatedUPCcode,whichisanumericalvalue.ThisUPCisthensenttothebackend

server(seeMobileApptoBackendServersectionunderCommunication).Thebackendserverthenassociatesthisitem’sUPCcodewiththenextreusableRFIDtagthatitdetectsbeingaddedtothefridgeandaddsthisitemtoitsinventory.

10 TESTING

SimulatedFridgeSystemInordertorigorouslytesttheSmartFridgeSystemweneededawaytogenerateayearofusagedata.

Thistaskwasdifficultfornumerousreasons.Theprimarychallengewastodevelopamethodforgeneratinganitemhistorythatwouldaccuratelyrepresentanaverageperson’susagepatternsoftheSmartFridgeSystem.Intheidealsituationwewouldhavemonitoredseveralpeople’sfridgesoverthe

courseofayearandtakennoteofeveryitempassinginandoutofthefridgealongwithexpirationdatesofeachitem.Unfortunatelythislongresearchprocesseswouldnotbepracticalforthefourmonthdurationofourproject.Thealternativewastodevelopamethodtogenerateayearlonghistoryofitems

withoutexplicitlyspecifyingeveryparametermanually.

Generatingayear’sworthofgroceryitemsbyhandwouldbeadauntingandtedioustask.First,youmustselecteverysingleitemthatwouldappearinthehistory.Theitemmustbechosenappropriatelybaseduponwhatelseincurrentlyinthefridge.Forexample,itdoesn’tmakesensetohaveafridgefull

ofjustmeatorcondiments.Ateachinstanceintimethefridgeshouldcontainareasonablyrealisticbalanceofitems.Next,theentryandexittimesoftheitemmustbeexplicitlyspecifiedandcarefully

chosentorepresentareasonableamountoftimespentinsidethefridge.Theexpirationdatemustalsobespecifiedandchosenappropriatelybaseduponwhentheitementeredthefridge.Oneofthemostdifficultchallengesittohaveabalanceofitemstemporallyasitemsareconstantlybeingaddedand

consumed.Thisnecessityofbalanceisessentialtotestingthesmartfridgenutritionalmetricssystem.Withoutabalancedsetofitemstherewouldbenowayofknowinghowwellthenutritionalmetricssystemperformsastheresultswouldappearerratic.Inthecaseofafridgefullofcondimentsthe

nutritionalmetricwouldclassifythefridgeasextremelyunhealthy.Yetthissituationisobviouslynotusefulasmostlypeopledon’thaveafridgefullofcondiments.Clearly,handcraftingthehistoryitemlistwouldbeadifficulttask.Ratherthanexplicitlysettingallthenecessaryparameterswedecidedtomake


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somegeneralizedrequirementsthatmustbesatisfiedandthenusedrandomnumbergenerationtogetreasonablevalues.

Achievingarealisticsetofitemswithoutmanuallyspecifyingeachvaluerequiredasignificantamountof

thoughtanddesign.Weneedawaytosetsomegeneralguidelinesforwhatwasexpectedoutofthehistorylistandthenuserandomnumbergenerationtoexplicitlysetthevalues.Beforewecouldattempttofindasolutionweneededtoidentifywhatmadeahistoryitemlistrealistic.Wefirstbeganto

researchwhatapersonshouldbeconsumingiftheyhadarelativelybalanceddiet.Duringtheresearchphase,onnumerousoccasions,thesourcesspecifiedadietonaweekbyweekbasis.Thedecisionwasthenmadetohandconstructafewsetsofdatathatwouldconstituteaweek’sworthofgroceryitems.

Thiswaywecouldensurethateveryweekcontainedawell‐balancedsetofitems.Thefurtherassumptionwasthenmadethatgrocerieswouldbeboughtonaweeklybasis.Oncetheweeklyitemlistswereconstructedarandomnumbergeneratorwasusedtorandomlyselectaweek’sworthof

groceriestobeaddedtothehistorylist.Oncealltheitemswereputintothehistorylistthenexttaskwastospecifytheentryandexittimesandexpirationdates.

Entrydateswasadrasticallysimplifiedbythedesignsinceweagreedthataweek’sworthofgrocerieswouldbeboughtweekly.Therefore,everyconsecutiveweek’sworthofitemshadanentrydate7days

apartfromthepreviousweek’sworthofitems.Thenextparametertospecifywastheexittimeoftheitem.Thetimeofexitwasmoredifficulttospecifythantheentrytimesincethiswouldbedifferentforeveryitem.Intuitionwouldtellusthatifwewerebuyinggroceriesonaweeklybasisthentheitems

wouldbeconsumedonaweeklybasisalso.ItwouldbereasonabletoassumetheconsumptionoftheitemswouldfollowaGaussiandistribution.Itemswouldbemostlikelytobeconsumedpartwaythroughtheweek,withlessitemsbeingconsumedmuchearlierorlater.Ifwesetthemeanofthe

Gaussiandistributionto5daysaftertheentrytimewewouldthenseesomeitemswouldbeconsumedbeforeandafterthe5thday.Itfollowsthatasmallerpercentageofitemswouldbeconsumedverysoon

aftertheentrytimeandverylongafterthe5thday.ThisagreeswithourchoicetomodelthisbehaviorwithaGaussiandistribution.InordertodetermineareasonablestandarddeviationfortheGaussiandistributionweassumedthatmostoftheitemsshouldbeconsumedbythe11thdayaftertheentry

time.Withastandarddeviationof3wewouldensurethat95%oftheitemsareconsumedwithintheentrytimeand11thdayfromtheentrytime.Againthischoiceagreedwellwiththesituationweweretryingtomodel.Thethirdandfinalparameterweneededtospecifywastheexpirationdate.The

expirationdatewashandledinasimilarmannertotheexitdate.Theexpirationdateassumptionwasalittlemoreunrealisticthantheexittimesincetheexpirationdataisheavilydependentonthetypeofitem.Forexample,frozenfoodswouldlastmuchlongerthanunfrozenvegetables.Forourpurposeswe

arepreparedtoacceptthisparticularshortcomingofthemodel.Thesinglerequirementwemustsatisfyishavingsomeitemsexpirepriortoexitingthefridge.Weneededthisparticularsituationinordertotestalgorithmsusedtodetectexpireditemsinthefridge.Tosatisfythisrequirementwe

neededtodeterminetheappropriatemeanandstandarddeviationoftheGaussiandistribution.ThemeanandstandarddeviationoftheGaussiandistributionfortheexpirationdatesshouldhavesomeoverlapwiththeGaussiandistributionusedfortheexitdates.Wewantedtheupper2.5percentofthe


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exitdatestofallwithinthelowest2.5percentoftheexpirationdates.Toachievethis,themeanwaschosentobe21daysfromentrytimewithastandarddeviationof3.

Throughresearchandunderstandingofthecharacteristicsinabalancedgrocerylistandhuman

behaviourwewereabletoavoidatedioustaskwithamoreelegantsolution.Recognizinghowtomodeltherandomnessofthesituationtogetherwithguidelinesandrestrictionswewereabletoaccuratelysimulateayearlonghistoryofgroceryitemsforanindividual.

Usingthismodelwewillbeabletodevelopanumberofdifferentrandomconsumptionhistorieswhich

wewillthenartificiallyinsertintotheserverfortestingpurposes.Theseartificialhistorieswillbeusedtotestthemobileappandthewebsite.Weplantotesteachofthefeaturesofboththewebsiteandthemobileapp(seeWebPresentationandMobileAppsectionsinourRequirementsDocumentor

MobileAppandWebServertoBackendServerCommunicationssectionsinthisdocument)usingatleasttwentydifferentartificialhistoriesinordertomakesurethatallofthedesiredinformationintheseexamplehistoriesiscommunicatedaccuratelyandeffectivelytotheuser.

AfurtherseriesoftestswillbeconductedusingtheentireRFIDSmartFridgesystemwhereRFIDtagged

itemswillbeplacedinandremovedfromthefridgebyourteammembersoverthecourseofseveraldayswiththeentiresystemupandrunning.Awrittenlogwillbekeptofallitemsaddedandremovedfromthefridge.Attheendofthetestperiodthisdatawillbecomparedwiththedatafoundinthe

serverandthedatadisplayedbythemobileappandthewebsitetoinsurethatthesystemisworkingasspecified.

Inaddition,aseriesofunexpectedbutpossibletestcases(listedbelow),suchasmalformedrequestbeingsentfromthemobileapptothebackendserver,willbetestedinordertoinsurethatthesystem

willnotcrashunderanycircumstances.

Finally,ausabilitytestwillbedevelopedbasedonthefinalRFIDSmartFridgeproductandtestsubjectsunfamiliarwiththeRFIDSmartFridgewillbeaskedtousetheproductandgivefeedback.Thiswill

insurethatourengineersdon’toverlookanyusabilityissuesbecausetheyaretoofamiliarwiththesystem.WewillanalyzethisuserfeedbackanduseittoinsurethatallaspectsoftheRFIDSmartFridgeareeasyandconvenienttouseandunderstand.

CommunicationTestingIntegrationtestingwasperformedthroughverifyingprocessesthatinvolvecross‐component

communication.Alltestsoutlinedbelow:

BackendServerTesting• Allpathsweretested(Table3)

o Server‐sidebehaviorverifiedo Responsebehaviorverified

• Non‐existentpathsweretested

o Errorresponsebehaviorverified


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InFridgeHardwaretoBackendServerCommunicationTesting• Sendingsetsofitems,verifyingresponse(HTTPcode200–OK)andserveraction

o Testhandlingofsetsofvarioussizes: Emptyset

Singleitemset Multipleitemset(10)

• SendingHTTPrequeststoaninvalidpath,verifyingresultingerrorresponse

iPhoneApplicationtoBackendServerCommunicationTesting• iPhonesendsaSHOWrequesttotheserver,parsesresponse

• iPhonesendsmalformedrequesttoserver,handleserror• iPhonesendsaleftoverlabelthroughaADD_OBJECTrequest,receivescode200(OK)response• iPhonesendsaUPCcodethroughaADD_OBJECTrequest,receivescode200(OK)response

• iPhonesendsmalformedADD_OBJECTrequest,receives400(BadRequest)response

WebServertoBackendServerCommunicationTesting• Verifytime‐sensitivewebpagesareupdated(dateschangeaccordingtothecurrentdate)• Verifyplotdataasseenonthewebpageiscorrectlypopulated• EnsurewebpagesupdateafterHTMLisregenerated(updated)asaresultofBackendServer

events

11 CONCLUSION

This document describes in detailed the proposed design for the RFID Smart Fridge. This design will be adhered to as closely as possible during the development of the RFID Smart Fridge prototype system. This will insure that all parts of the design are coherent and that no aspect is overlooked. The test plan will insure that all desired functionality of the RFID Smart Fridge is achieved and that no bugs exist in the software. This design provides clear goals for the development of the RFID system and prototype and will allow us to complete the system on schedule by December 7, 2011.


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12 REFERENCES

[1] RPagliara,DJungic,MJoblin,andSVerner,"RFIDSmartFridgeFunctionalSpecifications,"ENSC305,2011.

[2] AIMGlobal.(2010)RFIDGlossary.[Online][lastaccessedNov.20th,2011].http://www.aimglobal.org/technologies/rfid/rfid_Glossary.asp

[3] GS1.(2011)EANUPCbarcode.[Online][lastaccessedNov.20th,2011].http://www.gs1us.org/standards/barcodes/ean_upc

[4] technovelgy.com.(2010)HowRFIDworks.[Online][lastaccessedNov.20th,2011].http://www.technovelgy.com/ct/Technology‐Article.asp?ArtNum=2

[5] USFoodandDrugAdministration.(2010,Jan)FDAstudydeterminesRFIDeffectsonimplantedcardiacdevices.[Online][lastaccessedNov.20th,2011].http://www.rfidnews.org/2010/01/07/u‐s‐

food‐and‐drug‐conduct‐study‐to‐determine‐rfid‐effects‐on‐pacemakers‐and‐implanted‐cardiac‐devices

[6] RFID4SMEandtheEuropeanUnion,"IsRFIDsafeattheworkplace?,"EuropeanRFIDPlatform,Brussels,2008.

[7] MWardandRvanKranenburg,"RFID:Frequency,standards,adoptionandinnovation,"JISCTechnologyStandardsWatch,2006.

[8] GlassFish.(2011)JAXBReferenceImplementation.[Online][lastaccessedNov.20th,2011].jaxb.java.net

[9] SimpleUPC.(2010)SimpleUPC‐ProductLookup.MadeSimple.[Online][lastaccessedNov.20th,2011].simpleupc.com

[10] RFielding,JGettys,andJMogul.(1999)HypertextTransferProtocol‐‐HTTP/1.1.[Online][last

accessedNov.20th,2011].http://www.w3.org/Protocols/rfc2616/rfc2616.html

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