Use of UML and Model Transformations for Workflow Process Definitions

Use of UML and Model Transformations for Workflow Process Definitions

Audris Kalnins, Valdis VitolinsUniversity of Latvia, IMCS

Baltic DB&IS '2006, July 3-6, Vilnius, Lithuania

Agenda● Current workflow modeling topics

Required aspects of workflow definition

Workflow definition languages

MDD approach with model transformations as a novel solution in business modeling area

● Adjusting UML Activity Diagram for workflow definition AD subset for workflow definitions, Workflow Profile for AD

● BPMN diagrams as another notation for workflows BPMN subset, adjustments and additions

● Demo AD to BPMN transformation

● Conclusion

Current workflow modeling topics

● Workflow systems: have become completely distributed and global,

rely on web services as an implementation platform,

converge with ERP and EAI systems,

but till have to support humans in their business activities.

● Many different authorities: bunch of organizations (W3C, WfMC, OMG, OASIS, AIM, ...),

heap of standards (UML, BPMN, BPEL, WSCL, WSCI, ebXML, ...).

● Only two of these standards provide an easy readable graphical notation for workflow processes:

UML Activity Diagrams (AD) and

Business Process Modeling Notation (BPMN),

therefore as a proof of technique AD and BPMN have been chosen.

“Workflow complete" workflow system requirements● Adequate description of the control structure of the process – support

for branching, decisions, parallelization, synchronization and loops.● Possibility to model data flows and to base decisions, looping and

branching on process data. Process data should support rich data structures.

● Possibility to define different types of tasks:

a) for invocation of a workflow subprocesses,

b) automated tasks, which are either executed by workflow engine directly (Script Task), or by some sort of automated software service (Service Task, e.g. for Web services),

c) tasks where a human performer performs the task with the assistance of a software application (User Task),

d) tasks which are expected to be performed without aid of the workflow system (Manual Task).

● Resource management – mainly, the definition and management of human task performers.

AD subset for workflow definition

AD notation has a vast majority of features, most of which make no sense for workflow definition. As a suitable subset for workflow modeling the following elements are chosen :

● Activities and OpaqueBehaviors● CallActions:

CallBehavior, CallOperation actions SendSignal, AcceptEvent actions

● ObjectNodes: ActivityParameter nodes Input and Output pins

● Variables with Read and WriteVariable actions● Control nodes (Initial, ActivityFinal, FlowFinal, Fork, Join, Decision, Merge)

● Control and Object Flows● ActivityPartitions, Interruptible Regions, Loop Nodes

Classes which have Workflow Profile (AD stereotypes) applied, are described in the format Class – Stereotype.

AD subset for workflow definitionActivities and Opaque behaviors

Activity - MainProcess represents an activity which is a separate workflow process

Behavior - ManualAction, UserAction, ScriptAction - stereotypes for definitions of manual, software-supported manual and automated tasks

Operation - ServiceOperation stereotype for web service operation

Manual actions

User actions

Script actions

Service actions (external automated tasks – web service operations ir our case)

AD subset for workflow definitionCallActions:

CallBehavior, CallManual, CallSript, CallUser, CallOperation Actions

(Serviceman)

Pick Products in Package

Order

After 1 d

(Serviceman)

ShipPackage Order

CheckProductForEach item in Order.items

CheckAndReserveItem

OrderProduct

[item.status=NotAvailable]

Order Order

[else]

[Order.s tatus=Filled]

Order

Order

[else]

[item.status=Waiting]

[item.status=Reserved]

(Sales)

MakeOrder

(Sales)

ReviewInvoice

Prepare Payment

ReceiveOrder

PrepareInvoice

Process Order

(Accountant)

Close Order

CheckAndReserveItem

OrderProduct

CheckProduct

(Serviceman)


(Serviceman)

ShipPackage

CallBehaviorAction – CallManualAction, CallScriptAction, CallUserAction – calls to stereotyped actions

CallOperationAction - CallServiceAction is an automated task, which means invoking an interface of an external software component

AD subset for workflow definitionSendSignal, AcceptEvent Actions

(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



After 1 d

SendOrder

InvoiceInvoice.orderId=order.id

SendCancelRequest

SendPayment

OrderOrder.id=order.id

AcceptEventAction - StartAcceptEventAction - a new activity instance is started (createInstance="yes" in BPEL). IntermAacceptEventAction only activates the suspended activity

Order

CancelReques t.orderId=order.id

CancelReques t

SendInvoice

Payment

Payment.orderId=order.id

SendOrder

AD subset for workflow definitionObjectNodes:

ActivityParameter nodes

InputPins and OutputPins

(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



Order

Order

AD subset for workflow definitionVariables, ReadVariable- and WriteVariableActions

(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



order:=Order

order : Order:=order

order : Order

:=order

order:=Order

AD subset for workflow definitionControl nodes:

Initial, ActivityFinal, FlowFinal, Fork, Join, Decision, Merge

(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



AD subset for workflow definitionControl and Object Flows

Order

order : Order

Prepare Payment

SendPayment

SendCancelRequest

(Sales)MakeOrder

SendOrder

order:=Order

Invoice

:=order

(Sales)ReviewInvoice

Payment Payment

Order

Invoice Invoice

Order

Order

[Order.s tatus=Cancelled]

Order

[Order.s tatus=Accepted]

Order

Order

Order

Order

(Serviceman)ShipPackage

(Serviceman)Pick Products in Package

CheckProduct

After 1 d

Order

Order

ForEach item in Order.items

CheckAndReserveItem

OrderProduct


Order Order

Order

[else]


[else]


Order


order:=CancelRequest

:=order

:=order

SendOrder

ReceiveOrder

(Accountant)Close Order

Order

Payment

CancelReques t

SendInvoice

Process Order

PrepareInvoice

order:=Order

Order

Order

Order

Order

[Order.s tatus=Accepted]

Order

Payment

Invoice

Invoice

Order

Order

[Order.s tatus=Rejected]

Order Order

Order

Order Order

CancelRequest

CancelRequest

AD subset for workflow definitionActivityPartitions, Interruptible Regions, Loop Nodes

(Serviceman)


Order

After 1 d

(Serviceman)

ShipPackage Order


CheckAndReserveItem

OrderProduct


Order Order

[else]


Order

Order

[else]



(Accountant)Close Order

ForEach item in Order.items





Partition - Performer represents a performer of a manual or user action

LoopeNode - ForEach with heavyweight extension – new ForEach.collection association for loop iterator.

Fragment of the AD metamodel

source of model transformation

yellow – original classes

orange - stereotypes

ObjectNode

Operation

Activi tyGroup

Activi tyNode

Component

OrgUnit

Position

ForEach

MainProcesspartnerName : String

ServiceOperationoperation : String

ClassifierElement

InputPin

VariableAction

ReadVariableAction

Activi tyEdge

OutputPinActivityPartitionname : String

InterruptibleActivityRegion

Interface

CallOperationAction

IntermAEActionuri : StringpartnerLink : Stringoperation : String

ValueSpecificationexpression : String

CallBehaviorAction

WriteVariableAction

AcceptEventActionValuePin

LoopNode

Variable

Performer

Action

OpaqueBehaviorbody : Stringlanguage : String

Activityname : String

Behavior

Class

WebServiceuri : StringparnerLink : String

EndSSAction

CallServiceAction

IntermSSAction

CallManualAction

CallUserAction

CallScriptAction StartAEAction

ManualAction ScriptActionUserAction

context0..1 ow nedBehavior*

node *

base$OpaqueBehavior

ex tension$UserTask ex tension$ScriptTaskex tension$ManualTask

edge*

activity

class0..1nestedClassifier

*

input

*

bodyPart1

outgoing*source1

0..1

result1

output*result1

0..1

value1

test0..1

setupPart0..1

interface 0..1 ow nedOperation

*

class0..1

ow nedOperation *

ex tension$UserTaskex tension$ScriptTask

base$CallBehaviorAction

ex tension$ManualTask

ex tension$IntermSSAction

base$CallOperationAction

ex tension$Serv iceTask

ex tension$EndSSAction

containedNode*inGroup0..1

*

represents0..1

activityScope0..1

variable *

incoming*target 1

containedEdge

*

interrupts 0..1

interruptingEdge*

operation1

*

1 collection*

ex tension$IntermAEAction

base$AcceptEv entAction

scope0..1

variable* variable1

scope*

base$Componentex tension$WebServ ice

provided*

0..1value 1

base$Activ ityPartition

ex tension$Performer

base$LoopNode

ex tension$ForEach

activityGroup*

subGroup*

superGroup0..1

ex tension$Position

base$Class

ex tension$OrgUnit

guard1

behavior0..1

*

base$Operation

ex tension$Serv iceOperation

base$Activ ity

ex tension$MainProcess

BPMN subset for workflow definition

Similarly to the AD, BPMN also has unnecessary redundancy. Therefore as a suitable subset the following elements (which have natural semantics and mapping to BPEL) were chosen:

All types of ActivitiesUser, Service, Manual, Script Tasks, Embedded and Independent

Subrpocesses, LoopActivity Receive and Send Tasks for for receiving and sending

messages in non-interrupt situations Start and End Events, TimerIntermediate and

IntermediateEvents, attached to the boundary of an Activity ("interrupt construct")

All kinds of Gateways Properties and property Assignments

While the implicit BPMN metamodel is quite acceptable, the BPMN graphical notation lacks some important elements. Therefore for some elements new graphical notation is introduced.


Following the BPMN style the following elements are used in model, but are not shown graphically:

Input/output Messages for tasks (analogs to AD pins), Implementation related aspects (e.g., service operation, URI).

Dropped elements: Intermediate events other than timer and "interrupt construct", Data Objects, MessageFlows

BPMN Property it is not sufficient for modeling rich data structures, therefore BPMN is supplemented with UML Class diagram similarly to AD.

BPMN subset for workflow definitionAll types of Activities:

User, Service, Manual, Script, Send, Receive Tasks

Independent Subprocess, LoopActivity

Task type is shown as task icon:Hand – manual,”S” – script, arrows – service, hand+arrows – user task, loop – loop activityTask performers are shown in another compartment

MakeOrder

performers: Sales

ReviewInvoice

performers: Sales

Prepare Payment

Prepare Invoice

Receive Order

Process Order

Close Order

ForEach item IN order.items

CheckProduct


performers: Serviceman

ShipPackage

performers: Serviceman

BPMN subset for workflow definitionAll types of Activities:

Receive and Send Tasks for receiving and sending messages in non-interrupt situations

Convex flag – Send task, concave flag – Receive taskSimilarly to AD, data join criteria are shown as Annotations (an analog to Notes in AD)

Order

Invoice

order.id=invoice.orderId

CancelReques t

Payment

Order

sorder.id=order.id

Invoice

Payment

Payment.orderId=order.id


All types of Activities:Embedded subproces for interrupt construction

BPMN subset for workflow definitionStart, End Events, TimerIntermediate Event, and IntermediateEvents,

attached to the boundary of an Activity ("interrupt construct")


Properties and Assignments

Property is shown as a rectangle containing name:typeAssignment is shown as a thick arrow

order : Order

order := Order

order : Order

order := Order

order := CancelRequest


All kinds of Gateways


Sequence Flows

Customer Process

order := Order

Invoice

CancelReques t

Order

Payment

Prepare Payment

ReviewInvoiceperformers: Sales

MakeOrderperformers: Sales

Order

order.status=Cancelled

order.status=Accepted

Supplier Process

Close Order

order := Order

Receive Order

Payment

Prepare Invoice

Process OrderInvoice

order := CancelRequest

order.status=Rejected

order.status=Accepted

Process Order

CheckProduct

ForEach item IN order.items

Pick Products in Packageperformers: Serviceman

ShipPackageperformers: Serviceman

order.status=Filled

else

BPMN MetamodelTarget for model transformation

(subtypes for events are not shown)Process

name : StringprocessType : isAdHoc : Boolean

Propertyname : Stringtype : String

SequenceFlowconditionType : ConditionTypeconditionExpr : String

SupportElementname : String

PropertyMapexpression : String

Message

Assignmentexpression : StringassignTime : String

f

Participant

y

ReceiveTaskinstatiate : Booleanimplementation : String

ScriptTaskimplementation : String

Activi tyloopType : LoopTypeloopCondition : StringloopMaximum : Integer

BusinessProcessname : StringObject

Pool

SendTaskimplementation : String

Role

EntityTask

ManualTask

UserTaskimplementation : String

IndependentSubprocessisTransaction : Boolean

FlowObjectname : String

Event

GateGatewayStartEvent

MessageStartEvent

MessageEndEvent

MessageIntermedEvent

TerminateEndEvent

ServiceTaskimplementation : String

EmbeddedSubprocessisTransaction : BooleanisAdHoc : BooleanisCompensation : Boolean

assign *toProperty1

diagram1connections *

role1

objects

*pool1

* assignments

activity 0..1

properties

*

diagram

1

containedProcesses*

0..1

assignments*

process0..1

properties*

1

graphicalElements*

out*

source1

in*

target1

pool0..1

process0..1

entity1

0..1inMessage

0..10..1

outMessage 0..1

*

performers1..*

*

performers1..*

subProc1

inputMaps*

subProc1

outputMaps* to1

from1

message0..1

properties*

map

mappedProperty

caller*

diagramRef1

0..1

assignments*

1gates

*

pools *

participant1

1

pools 1..*

pk: Package

a: Activity

bp: BusinessProcessname := a.name

proc: Processname:="Process:"+a.name

pool: Poolname:=a.nameboundaryVisible:=true

{Activity = BusinessProcess + Pool + Process}

packageelement

packageelement

processsrc

dst

package

element

package

element

pools

Transformation as effective solution for AD to BPMN mappingThough graphical presentation looks similar, transformation is not trivial due to

conceptual differences between AD and BPMN:

toBp: Bus inessProcessact: Activ ity

intermss: IntermSendSignalAction

sendtask: SendTaskoper: Operation

param: Parameter msg: Messagename:=param.name

{IntermSendSignalAction+Operation+(WebService) = Task}

activity

dst

_objectDiagram

_bpObjec ts outMessage

operationCaller

operation

src

dstoperation

ow nedParameter

. . .

. . . . . .

More about MOLA:Tomorrow (July 5) 13.00, Session 4 A (Research Track, Room 1: Auditorium 03),Simple and Efficient Implementation of Pattern Matching in MOLA Tool

Pattern part

. . .

if low : _InterruptingFlow

embproc: EmbeddedSubprocessfrom_object: Object

@from_object: Object

@embproc: EmbeddedSubprocess

@iflow : _InterruptingFlow

@from_object: Object

{Change source of interrupting flow from contained node to embedded subprocess}

_containedObjects_inEmbSubprocess

source

outgoingsource

_containedObjects_inEmbSubprocess

sourceoutgoing

ForEach loop

Loop body

Action (create) part

Loop variable

Rule with Pattern

Demo

Conclusion

● When there is no single standards (for languages, techiques and platforms),only model driven development (MDD) approach with model transformations permits to use all the notations (the most appropriate one for each case).

● For model transformations precise modeling language semantics is necessary.As it was shown with UML AD and BPMN, standards should be adjusted and profiled.

● Metamodel-based generic modeling tools for MDD approach is of high demand, however there is no adequate industry support for that.Therefore development of new generation of metamodel-based and model transformation-ready tool is started at UL IMCS.

Questions and Answers

Use of UML and Model Transformations for Workflow Process Definitions

Documents

workflow definitions

workflow processes

workflow definitionactivities

workflow subprocesses

workflow engine

workflow definitionad

workflow definitionad

workflow system manual