自动售货机需求报告.docx

自动售货机需求报告.docx

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自动售货机需求报告

VendingMachine

1-Objectives

Theobjectivesofthisexerciseareto:

∙BasedonTOODdesignapproach,propose2solutionsforthedesignarchitectureoftheVendingMachinepresentedinspecificationmodule:

∙Firstsolution:

sequential-withoutprocess.

Usingasequentialsolution,itisinterestingtoshowthanonemodeoftheStateTransitionDiagram（STD）cannotbereached:

“DispensingProduct”.

∙Secondsolution:

concurrent-withprocess（es）.

Hypothesismustbemadeonthehardware.

2-ProblemOverview

ThisexampleisanextensionoftheproblempresentedattheForum”StructuredDevelopment”inSanFrancisco,inFebruary1986.

Theproblemstatementandtheresultingmodelswereinteractivelydevelopedanddescribedasadialoguebetweenthecustomerandtheanalyst.

Thecustomerstartedbyoutliningtotheanalystthatheisfacedwithcrooksascustomerswhotryputtingjunkintothecoinslotsofhisvendingmachineshopingtogetsomethingfornothing.Someeventrytoentercoin-likeslugstofoolthemachines.Theyalsotrytovandalizetheselectionregistertogetproductsfree.Thesearemajorproblemsforthevendingmachineoperatorsbecausetheydobusinessonanarrowmargin,whichdisappearsveryquickly.Themachineistodothefollowing:

-Acceptobjectsfromthecustomerinpaymentforhis/herpurchase.

-Checkeachobjecttomakesurethatitisnotaslug.Thisistobedonebyvalidatingthesize,weightandthickness.

-Acceptnickels,dimesandquarters.Anyothercoinsaretobetreatedasslugsandreturnedtothecustomer.

-Onlyinitiatepaymentcomputationorproductselectionprocessafteravalidatedcoinisdetected.

-Acceptproductselectionfromthecustomer.

-Checktoseewhethertheselectedproductisavailable,ifnotavailable,returncoinsautomaticallyandnotifycustomer.

-Acceptavarietyofproducts,whichwillchangefromtimetotime.Hence,theproductpricesshouldbechangeable.

-Returnthecustomer’spaymentonrequestifheorshedecidesnottomakeaselection.

-Dispensetheproducttothecustomerifitisavailableandtheamountissufficient.

-Returnthecorrectchangetothecustomeriftheamountdepositisgreaterthantheproductprice（initialconditions?

）.

-Disabletheproductselectionaftertheproductisdispensedanduntilthenextvalidatedcoinisreceived.

Severalextrarequirementscouldbeaddedtothefirstlistofuser’srequirements,sinceweidentifiedsilences:

-Rejectcoinsasslugduringtheproductisdispensed.

-Haveavailablecoinstobeabletogivebackthechange（initialconditions）.Forthat,thecoinsintroducedbythecustomerareaccumulatedinthecoinsstorage（Anywaywedon’tknowiftheinsertedcoinsareusedforgivingbackthechangeornot）.

-Toleranceforvalidatingthethickness,size&weight（doesn’thaveeffectonthearchitecturenoronthealgorithms.

-Rejectcoinsasslugifthereisnotenoughchangeandofcoursedoesn’tdelivertheproduct（dowehavetheinformationfromthehardware）.

-Rejectcoinsasslugifthereisnospaceenoughinthereceivingbox（dowehavetheinformationfromthehardware）.

3-Proposedcontextdiagram

Sincenoinformationonthehardwareisavailable,thefollowingcontextdiagramisproposed（asfunctionaldiagram;nolowlevelexchanges）.3differentterminatorsareproposed:

-COINSSYSTEM:

thesystemforprocessingtheobjectsandcontainingthecoinscontainer,

-SELECTOR:

theinterfaceforthecustomer’sactionsandnotifications,

-PRODUCTDISPENSER:

theboxcontainingtheproducts.

SincethereisnoindicationoftheinitialnumberofproductsfromthePRODUCTDISPENSERandtheinitialnumberofcoinsfromtheCOINSSYSTEM,assumptionsmustbemaderegardingthelimitandinitialconditions.Thesevaluesaredefinedbycompilation（#defineofC）.

-Eachvalidobjectissentdirectlytothechangecoinsstorage（ifspaceavailable）andwillbeusedaschangecoin.

-Onechangestorageisavailableforeachtypeofcoinandfullassoonasthevendingmachineisturnedon.ThemaximumvalueisMaxNbOfCoin,sameforeverystorage.

-ThenumberoftypeofproductisdefinedbyMaxTypeOfProductsandthemaximumnumberofproductforonetypeisdefinedbyMaxNbOfProducts.

-AssoonastheVendingMachineisturnedon,theproductstorageisconsideredfullforallproducts（typeandnumberfor1type）.

-ThedataflowcalledslugisinfactacontrolflowbecauseaneventotheterminatorCOINSSYSTEM.

RecalloftheStateTransitionDiagram

4-Identificationofobjectsandclasses

4.1Classes

FromthetextbeforeandtheglobalSARTmodelpresentedinspecification,thefollowingobjects,classesandfunctionscanbeproposed.

EntityName

Attributes

Type

Object

Thickness（integer）

Size（integer）

Weight（integer）

T_Object

Coin

Object

Value

Type

T_Coin

Payment

Payment

Integer

Product

Identifier

Price（integer）

T_Product

Mode

Mode

T_Mode

4.2Instantiation

Theinstantiationofaclassbecomesanobject.Inthecaseofthevendingmachinethereare:

Coinsstorage=multipleinstantiationoftheclassCoin,

Productsstorage=multipleinstantiationoftheclassProduct,

CurrentPayment=singleinstantiationoftheclassPayment,

CurrentMode=singleinstantiationoftheclassMode.

4.3Externalinterfaces

1terminatoristranslatedin1TOODentitysuchasmachine,sub-applicationorprocess.InthecaseoftheSARTdiagramabove,3machinesareidentified.

5-Functionality

Entities

Function（methods）

Parameters

Coins

-Validate

-Input=object

-output=Value,status（coinorslug）

-Accumulate

-Input:

Coin

-Output:

status（full）

-ReturnCoins

-input:

Change

-Output:

Status（enough,notenough）

Payment

-Accumulate

-Input:

CoinValue

-Output:

none

-Get

-Input:

none

-Output:

Payment

-Clear

-Input:

none

-Output:

none

-Validate

-Input:

ProductPrice

-Output:

Status（enough）

Products

-Dispense

-Input:

ValidSelection

-Output:

Status（OK/NOK）

-GetPrice（Validation）

-Input:

Selection

-Output:

Price,Status（OK/NOK）

Mode

（Containedinthemaincontroller）

ADT_Object

-Initialize

（Questionforthestudents–why?

）

-Input:

Thickness,Size,Weight

-Output:

Object

-IsEqual

-Input:

Object1,Object2

-Ouput:

Status（Equal/NotEqual）

ADT_Coin

-GetValue

-Input:

Coin

-Output:

Value

-Validate

-Input:

Object,

-Output:

6-FirstProposedsolution:

sequentialcase

Note:

Theproposedsolutionhereafterisnottheonlyonepossible.Severalsolutionsexist,andthedesignerhastochoosethebestoneregardingtheencapsulation,abstraction,…Especially,theprocessofthinkingmakesusbeginwiththeresearchofthemostelementaryobjectsbeforegroupingthem.

Theprocessisbottom-up.

6.1Architecture

Figure1:

ApplicationArchitecture

2sub-applicationsappear:

Coins&Products.

Thesub-application“Coins”isverybigcomparedto“Products”andtothemachinesSELECTOR&Payment.Butthegroupingofrelatedentitiessuchasobject,coins,terminatorcoinssystemobligesthedesignertochoosethissolution.Ofcoursethebalanceofthedesignmustalsobestudiedandothersolutionscanbeproposed.Justificationsmustthenbegiven（worksharingforexample）.

Thesub-application“Products”containsonly2entitiesthatareamachineforthestorageandanADTforthetypeproduct.WithTOOD,wecouldhaveonlyonemachinefor“Products”definingboththestorageandthetype（seetheGDLTOOD）.But,ifwetakethecaseoftheC++language,itrequiresabsolutelyfirstthedefinitionoftheclassandsecondtheinstantiation（s）ofthisclass.AndanywaythetranslationfromSARTtoTOODproposestotranslatedataflowsintoAbstractDataTypes.

Note:

Fortheentity“Products”,thefunction“Validate”returnsthepriceoftheselectedproduct.Afunctioncouldexist（“GetPrice”）togetthisvalue.Itcanbeeasiertounderstand.

Note:

Anothersolutionistogroupalltheexternalinterfaceswithin1entitytomakeeasierthemaintenanceandbettertheportability.

6.2MachineMODE–Interfaces&Environment

ItisnotnecessarytodrawagainthediagrambecauseitwouldbeveryclosetoFigure1.

6.3Sub-application“Coins”

6.3.1Interfaces&Environment

6.3.2Bodyofthesub-application

Thebodyofthissub-applicationisrelatedtodetaileddesign,everyentitycomposingthesub-applicationbeingabasicone.

ADT_ObjectisusedbyADT_Coin（via“IsEqual”）andCOINSSYSTEM（via“Initialise”）.Thequestion“Whydoweneedthisfunction?

”canbeaskedtothestudents.

6.4Sub-Application“Products”

6.5Machines“Payment”&“SELECTOR”

Wedon’tknowtheinterfacesoftheSELECTOR.

Thequestionsthatcanbeaskedare:

∙Isitpossibletoreadwithoutwaittheselection?

∙Whatisthehardwarefortheuser’slamp（notavailable）,timeout,on/off?

6.6MainAlgorithm

/*ProposalofAlgorithmforthemain（）*/

Mode=Wait_For_Coin

Payment.Clear（）

while（true）do

wait1secondNotreallynecessaryinthatcasebecausetheCPUisdedicatedtothe

vendingmachine

if（GetValue（OutValue）==OK）

|Payment.Accumulate（InValue）

|Mode=Wait_For_Selection

endif

if（SELECTOR.AcceptSelection（OutSelection）==true）

|if（Mode!

=Wait_For_Selection）donothing

|else

||if（Products.GetPrice（InSelection,OutPrice）==AVAILABLE）

||if（Payment.Validate（InPrice,OutChange）==OK）

||if（Coins.ReturnCoins（InChange）==OK）

||Mode=Dispensing_Product

||Product.Dispense（InValidSelection）/*Returnedstatusnotused*/

||else

||Payment.Get（OutCurrentPayment）

||Coins.ReturnCoins（InCurrentPayment）

||endif

||Payment.Clear（）

||Mode=