papazoglou webserv 2e cs solution notes part3

8/13/2019 Papazoglou Webserv 2e Cs Solution Notes Part3

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ServiceOrientedArchitectureCaseStudy

Part3SOAImplementationoftheAVERSCaseStudy

Part-3SOAImplementationoftheAVERSCaseStudy

1Introduction

Thisreportaimsatthedescriptionoftheinitialstepsfortheimplementationofatop

down ServiceOrientedArchitecture (SOA) approach to theAVERS SupplyChain case study,

whichwasdescribedindetailintheliteraturereviewofthefirstassignment.

On the secondassignment,ahigh levelmodelof thewholeAVERS supplychainhas

beenbuilt,depictingthebusinessprocessesthatruletheentirechainfromthesupplypartto

the distribution of the final products, passing through the manufacturing activities. The

BusinessProcessModel&Notation(BPMN2.0)hasbeenusedtomodeltheprocessesand,asa

second step, thebusiness servicesneeded toenable the interactionsbetween thepartners

weredescribedintermsoftheirinterfaces,inputsandoutputs.

Finally, when it comes to this third assignment, further details regarding the

implementationof theproposedmodels are given.TheWeb ServicesDescription Language

(WSDL) files are designed for the business services, therefore identifying their constituent

operations and required parameters, as well as the Business Process Execution Language

(BPEL)filesfortheorchestrationofsuchservices.

Thisdocument,thus,describestheresultsachievedoneachstepofthedesignofthe

initial implementationdetails fortheAVERSSOAapproach.First, theaforementionedWSDL

andBPEL

files

are

implemented.

Then,

the

designed

BPEL

processes

are

enhanced

with

transactionorientedfeaturesbytheuseofscopes,faultandcompensationhandlers.Finally,a

discussion of how the designed BPEL processes fit into the previously designed BPMN

processesiscarriedout.

Note:

The processes Product inventory control and Product Shipment Administrationand

Production Controlare identified to be the richest of the processes. They contain most

possibilitiestoshow,howBPMNprocessescanberefinedandimplementedusingBPEL.They

alsocontain interactionwithexternalpartners, thusproviding transactions.Compensation is

modelledexplicitly,

as

well

as

fault

handling.

These

processes

are

modelled

with

all

needed

assignactions, instantiating all variables correctly. All activities that imply any message

exchange like the invoke and receiveactivityare implementedbasedon thecorresponding

WSDLfiles.Thus,correctoperationsareassigned totheseactivities. Itshouldbepossible to

come up with an executable version of these BPEL processes, needing little effort. (The

servicesneedtobeimplemented,ofcourse.)

Theother twoprocesses (OrderProcessingandProductionSchedulingandMaterialControl

andProcurement)areonlymodelledasskeletons.TheycanbemappedproperlytotheBPMN

models but they are not ready to execute. They do not contain valid assigncode and the

operationsare

not

mapped

to

the

corresponding

WSDL

files.

(But

these

files

are

provided

and

describedhere.)


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This thoughtfuldecisionwas takenbecauseofexternal time constraints.Because it is truly

believedthatthetwoaforementionedBPELprocesses(ProductinventorycontrolandProduct

Shipment Administration and Production Control) show in detail the pitfalls andmappings

fromBPMN

to

BPEL,

this

approachwas

taken

and

to

be

considered

acceptable.

2ImplementationoftheWSDLDescriptionsandBPELProcesses

In thissection, thevariousWebServices required for theAVERSSupplyChainare identified

and designed corresponding to the core processes defined in Assignment 2 as per the

ANSI/ISA95sfunctionalflowdatamodel.Then,fourBPELOrchestrationprocessesaredefined

with respect to the fourbasicprocessesof theSupplyChain.A totalof twelveWebService

DescriptionLanguage(WSDL)filesaredefinedcorrespondingtothefourbasicprocesseslisted

below:

OrderProcessingandProductionScheduling:

OrderManagementServices:OrderManagementService.wsdl CustomerRelationshipManagementServices:CRMService.wsdl

ProductionControl:

ProductionRequestServices:ProductionRequestWS.wsdl ProductionRuleServices:ProductionRuleWS.wsdl ProductionLineServices:ProductionLineWS.wsdl RawMaterialServices:RawMaterialWS.wsdl

MaterialControlandProcurement:

InventoryManagementServices:InventoryMgmtWS.wsdl MaterialRequestServices:MaterialRequestWS.wsdl SupplierRelationshipServices:SupplierRelationshipWS.wsdl NotificationServices:NotificationWS.wsdl ExternalSupplierServices:ExternalSuppliersWS.wsdl

ProductinventorycontrolandProductShipmentAdministration:

CustomerServices:ProductInventoryControlCustomerServices.wsdl CarrierServices:ProductInventoryControlCarrierServices.wsdl ProcessinternalServices:ProductInventoryControlProcessInternalOperations.wsdl

FortheProduct inventorycontrolandProductShipmentAdministrationprocess,aWSDLfor

internal services has been designed. BPMN provides the concept of tasks,whichwas used

whenmodelling.ThisconceptcannotbetransferredtoBPEL,sinceBPELbasicallyknowsonly

theinvokeactivitytodosomeprocessing.Internalexecutionofscriptsordatacollectionisnot

possible. Thus, the internal service provides operations like data collection for the BPEL

process.Furthermore,theoriginallydescribedWSDL(inAssignment2) issplit intwopartsto

clearlyshowtheimpactofexternalcollaborators.Inthiscase,thereisacarrierserviceswhichprovides interaction with external carriers and a customer service for the customer


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interaction.Note that there isonlyoneWSDL for all carriers. It isassumed thatall carriers

providethesameoperationsanddataschema.

AlltheWSDLsaredesignedusingtheTopDownapproachwiththehelpoftheEclipseWSDL

Editor.Thedetailsregardingtheoperationsinputandoutputstructure,ofeachWebServicehasalreadybeendescribedinAssignment2,andhasnotbeenexplainedhereagain.ModelingProcedure:

This sectiondescribes theprocedure thatwas followed tomodel theWSDLsusing theTop

Down approach using the Eclipse Editor. Only the Order Management Service has been

describedindetailhere,andthesamemethodologywasfollowedtomodelalltheremaining

WSDLs.

Definitionof

Operations:

Figure1:WebServiceOperationsDefinition


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DefinitionofInputandOutput:

Figure2:InputandOutputDefinitioninWSDL

DefinitionofCustomTypes:

Figure3:MessageTypeDefinitioninWSDL


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3ImplementationofTransactionsandCompensationsinBPEL

Themain

focus

on

transactions

was

given

to

transactions

with

external

partners.

Scopes

are

definedaroundtheactivitiesthatexecutetransactions.Anexampleisgivenherebasedonthe

ProductinventorycontrolandProductShipmentAdministrationprocess.

Figure4:ScopeandCompensation

Theredframeabovemarksthescopeinapartoftheprocess.Withinthescope,aselected

routeis

booked

with

an

external

carrier.

This

transaction

is

modeled

in

an

asynchronous

style.

Incaseanythinggoeswrongwithinthisscope(ortransaction),thisbookinghastobe

compensated,whichisshownintherightpart.Compensationisdoneinthiscasebenotifying

aninternalprogramaboutthiserror.Then,furthercompensationispropagated,incaseother

activitieshavetobecompensated.Anerroristhrown,becausewithoutcarrier,theprocess

cannotcontinueandterminatesuccessfully.Manualactionisneededinthiscase.


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Figure5:Faulthandling

Anotherexampleiserrorhandling.Again,theleftsideshowsactivitieswithinascope.

Productsarepreparedforshipmentandwhentheyarehandedovertothecarrier,theprocess

getsanotification.Incasesomethinggoeswrongherewithinthisscope,e.g.theproductsare

nothandedovertothecarrierforanyreason,afaultisthrown. Aninternalnotificationissent

andcompensation

is

triggered.

Thus,

other

activities

or

scopes

that

implement

compensation

andarealreadycompletedarecompensatedthisway.Compensationaswellasfaulthandling

ispropagatedfrombottomtotop.Consequently,thebookingofacarrieriscanceled

automaticallybycompensationpropagation(seeexampleabove,whichisfromthesame

process).


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4RelatingtheBPELModelstotheBPMNModelsofAssignment2

Thissection

explains

how

the

BPEL

processes

that

are

designed

fit

into

the

BPMN

processes

thatweremodeledinAssignment2.FourcoreprocessesweredefinedinAssignment2asper

theANSI/ISA95s functional flowdatamodel,andoneBPMN2.0diagramwasmodelled for

eachofthesecoreprocesses. Inthisassignment, itwasdecidedtorelateeachofthese four

BPMNdiagramstoacorrespondingBPELprocess.

OrderProcessingandProductionScheduling ProductionControl MaterialControlandProcurement ProductinventorycontrolandProductShipmentAdministration

AllthefourBPELProcessesaremodelledintheAsynchronousmanner,withcorrelationsetsin

ordertomaintaincontextforasinglePurchaseOrderRequest.Thescopeandcompensation

sphereshavealsobeenmodelledineachoftheseBPELprocesses.

BPEL01OrderProcessingandProductionScheduling:

ThemainfunctionsofthisBPELprocessaretheCustomerOrderhandling,OrderAcceptance

and Confirmation. It involves verifying the order, registration of the order, verifying the

customerliquidity,checkingthetypeofcustomerinordertoconsolidatetheorderandfinally

preparingthefinalInvoice(orBill)fortheCustomer.


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Figure6:OrderProcessingProductionSchedulingBPELProcess


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BPEL02ProductionControl:

ThisBPELprocessperformsthemain functionssuchascheckingtheaccordanceofschedule

with

production

schedule

and

standards.

It

also

involves

performing

plant

engineering

activities and update of process plan. Furthermore, it also issues requirements for raw

materialsandtransformationofrawmaterialsintoendproducts.


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Figure7:ProdutionControlProcess

BPEL03

Material

Control

and

Procurement:


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Thisprocess isprimarilyaboutmanaging the inventory. Italsoperformsother functions like

managing transfersofmaterialandplacingorderswithsuppliers for rawmaterials,supplies,

spare parts, tools,equipment and other required materials. It also monitors progress of

purchasesand

performs

reporting

to

requisitioners.

Furthermore

is

also

handles

receiptof

incoming material supplies, and release incoming invoices for payment after arrival and

approvalofgoods.


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Figure8:MaterialControlProcurementBPELProcess


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BPEL04ProductinventorycontrolandProductShipmentAdministration:

ThisBPELprocessdealswithmanaginginventoryoffinishedproducts,makingreservationsfor

specific

product

in

accordance

with

product

selling

directives

and

organizing

transport

for

productshipmentinaccordancewithacceptedordersrequirements.Italsoinvolvesnegotiating

andplacingorderswith transport companies, and releasingmaterial for shipment.Finally, it

preparestheshipmentconfirmationandperformsinvoicingtobesenttothecustomer.


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Figure9:ProductinventorycontrolandProductShipmentAdministration

Basically,the

BPEL

process

shows

the

same

activities

like

the

BPMN

model.

As

mentioned

before,BPMNprovides the conceptof tasks,whichwasusedwhenmodelling.Thisconcept


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cannotbetransferredtoBPEL,sinceBPELbasicallyknowsonlytheinvokeactivitytodosome

processing.Furthermore,BPELdoesnotunderstandtheconceptofmultipleinstanceactivities

which are activities inBPMN that are executedmultiple times and inparallel. In this BPEL

process,thiswasmodelledasaforloopthatexecutesactivities inparallel.Itsrangedepends

ontheactivitybefore,thatmeanshowmanyactivitieshavetoberuninparallel.Theforloop

loopsexactlythatmanytimes,thusitisdetermineddynamicallyusingvariables.

Figure10:MappingofmultipleInstanceactivitiesfromBPMNtoBPEL

Furthermore,sometasksinBPMNhavebeenleftoutinBPELbecauseBPELdoesnotsupport

this conceptof tasks, asmentioned. These tasks inBPMNdidmostly somedata gathering,

gettingdatafromadatabaseforexample.Theideawastokeepthedataflowofeachprocess

instancelow

when

data

is

not

needed

frequently.

In

BPEL

however,

data

is

often

modelled

usingglobalvariables,thusbeingavailableduringthewhole instance life.Theseactivitiesare

notrepeatedlymodelledintheBPELsincetheywouldnotaddanyvalue.

5Conclusion

TheSOAimplementationprovidesaBPELmodelforasupplychainscenario.Basedon

previouslymodeled BPMNprocesses,BPELprocessesweremodeledandrefined.WSDLfiles

forseveralservicesinthedescribedsupplychainscenariowerecreated.

BPELisseenasavalidprocessmodelinglanguagetorefineaBPMNmodel.Executable

solutionscanbeachieved.However,thisdoesnotgosmooth.BPMNandBPELhavedifferent

scopesandthusdifferentcomplexity.BPMNinitsversion2.0providesmanynewmodeling

artifactswhichcannotbemappedeasilytoBPEL,e.g.simpletasks,humantasks,ormore

specifically,multipleinstanceactivities.Errorhandlingisevenmorecomplextomodelfrom

BPMNtoBPEL.Thus,itwasnoteasytomapallconceptsmodeledinBPMNtotheBPEL

processes.

BPELismissingfurtherevolvement.Sinceitslastversionsomeyearsagotherehasnotbeen

mucheffort

to

improve

the

language

further,

only

through

extensions.

So

any

modeling

of

a


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processisstillaquitecomplexandtimeconsumingprocess,howeverprocessescanbe

modeledsuccessfully(tobeexecutable).

6Acknowledgements

Theauthorwishestoacknowledgethefollowingstudentsfortheimplementationofthe

AVERSCaseStudy.

AjaySagar FbioCardosoCoutinho HolgerEdgarOviedoCahuata RodrigoDeOliveiraMachado SuriChandramouli TobiasHberle

papazoglou webserv 2e cs solution notes part3

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