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Process Modelling and Standardization
Jan MendlingDept. of IS and New Media, WU Vienna, [email protected]
Process Modelling and StandardizationFolie 2
Agenda
1. Business Process Management and Lifecycle
2. Process Design
• Process Implementation
• Conclusions
Process Modelling and StandardizationFolie 4
Why Processes and Workflow?
Old process New processReceive
Book Order
Wrap Book
Write Bill
Send Book
Check Credit Rating Reject Order
Receive Book Order
Wrap Book
Write Bill
Send Book
Process Modelling and StandardizationFolie 5
Why Processes and Workflow?
1st Reason: Flexibility
• Introduction of a separate process layer
• Functions tend to be stable
• Ordering of functions is subject to change
• Processes become more easy to adapt
Process Modelling and StandardizationFolie 6
Why Processes and Workflow?
Manual process Automatic processReceive
Book Order
Wrap Book
Write Bill
Send Book
Check Credit Rating Reject Order
20 min
5 min
15 min
20 min
5 min
Receive Book Order
Wrap Book
Write Bill
Send Book
Check Credit Rating Reject Order
0 min
0 min
1 min
5 min
5 min
Process Modelling and StandardizationFolie 7
Why Processes and Workflow?
2nd Reason: Productivity
• Waiting times between functions minimized
• Automatic routing of work items
Process Modelling and StandardizationFolie 8
Why Processes and Workflow?
more reasons:
• Better customer orientation
• Better controlling of processes
• Better documentation of enterprise
• Better communication between different departments
• Avoiding problems
• ...
Process Modelling and StandardizationFolie 9
Business Process Lifecycle
Process Metrics
other reportingpurposes
ProcessImplementation
ProcessDesign
Process Enactment
Process Evaluation
Process Models
Impl
emen
ted
Pro
cess
es
Mea
sure
s fo
r Im
prov
emen
t
Process Metrics
Mea
sure
-men
ts
Process Monitoring
Animation,Simulation
Metrics,Targets
Goals,Evironmental
Analysis,Organizational
Analysis
Targ
et V
alue
s
M. zur Muehlen: Workflow-basedProcess Controlling, 2004
Process Modelling and StandardizationFolie 10
Process Design and Implementation
Modelling Languages for Business Processes and Workflow
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 11
Workflow Terminology and Glossary
Business Process(what is intended to happen)
Process Definition(representation of what is intended to happen)
Workflow Management System(controls automated aspects
of the business process)
Process Instances(representation of what is actually happening)
Activities
is managed by
is defined by
composed ofSub-Processes
which may be
Manual Activities(which are not managed as
part of the Workflow System )
Automated Activities Activities Instances
Work Items(tasks allocated to a workflow participant)
Invokes Applications(computer tools or
applications used to support an activity)
or
via
Include one or more
which include
and/or
used to create and manage
WfMC: Workflow Glossary, 1999Design time
Runtime
Process Modelling and StandardizationFolie 12
Agenda
Business Process Design
Modelling Processes with Event-Driven Process Chains
Process Modelling and StandardizationFolie 13
Process Design and Implementation
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 14
Event-Driven Process Chains (EPC)
Receive Book Order
Start
Order received
Check Credit Rating
Rating negative
Rating positive
Reject Order
Write Bill
Bill written
Wrap Book
Book wrapped
Send Book
Book sent
Order rejected
Event
Function
Process Interface
Connectors
Control Flow Arc
EPC Symbols
Process Modelling and StandardizationFolie 15
Purpose of EPCs
• Documentation of business processes
• SAP implementation projects
• Business process re-engineering
Process Modelling and StandardizationFolie 16
EPC Semantics: Transition Relation
Events
Functions
AND Split
AND Join
OR Split
XOR Split
Cuntz, Kindler, 2004
Process Modelling and StandardizationFolie 17
EPC Semantics: Transition Relation II
OR Join
XOR Join
Non-local semantics
Process Modelling and StandardizationFolie 20
Conclusions
• Circles may lead to ambiguous situations
• It is a good choice to avoid circles and loops (if possible)
• Many Workflow Systems do not allow circles
• For more on EPCs, see www.epk-community.de
Process Modelling and StandardizationFolie 21
Agenda
Business Process Implementation
Standards and Languages for Modelling Workflows
Process Modelling and StandardizationFolie 23
Standardization Bodies
• OMG: Object Management Group
• WfMC: Workflow Management Coalition
• BPMI: Business Process Management Initiative
• OASIS: Organization for the Advancement of Structured Information Standards (+ UN/CEFACT)
• W3C: World Wide Web Consortium
• academic initiatives
Process Modelling and StandardizationFolie 24
BPM Specifications Overview
• BPDM: Business Process DefinitionMetamodel by OMG
• BPEL4WS: Business Process Execution Language for Web Services by OASIS
• BPML: Business Process Modeling Language by BPMI
• BPMN: Business Process Modeling Notation by BPMI
• BPSS: Business Process Specification Schema by OASIS + UN/CEFACT
• EPML: EPC Markup Language byacademia
• OWL-S by academia
• PNML: Petri Net Markup Language by academia
• UML ActD by OMG
• WS-CDL: WS-Choreography Description Language by W3C
• WSCI: WS Choreography Interface byW3C
• WSCL: WS Choreography Language byHewlett-Packard
• WSFL: WS Flow Language by IBM
• XLANG by Microsoft
• XPDL: XML Process Definition Language by WfMC
Process Modelling and StandardizationFolie 25
Comparison of BPM Specifications
BPD
MB
PEL4
WS
BPM
LB
PMN
BPS
SEP
ML
OW
L-S
PNM
LU
ML
Act
.D.
WS-
CD
LW
SCI
WSC
LW
SFL
XLA
NG
XPD
L
Task I/OTask Address
ProtocolControl FlowData Handling
Instance IdentityRoles
Quality Attributes
EventsExceptions
TransactionsGraphic PositionStatistical Data
? + + + + - + - + + + + + + +? + + + - - + - - + + + + + +
? + - + - - + - - + + + + + -? + + + + + + + + + + + + + +? + + + - - - - + + - - + - +? + + - - - - - - - + - + + -? + + + + - + - + + + - + + +
? - - - + - + - - - - - + - -
? + + + - + - - - - - - + + +? + + + + - - - + + + - + + +? + + + + - - - - + + - - + -? - - + - + - + + - - - - - -? - - - - - - - - - - - - - +
Mendling et al.: A Comparison of XML Interchange Formats for BPM, 2004
Process Modelling and StandardizationFolie 26
Process Design and Implementation
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 27
Concepts used in BPEL4WS
• Partner Links:• Bilateral conversation (my Role, Partner Role)• Interface requirements of partners
• Data and messages:• Variables• Properties• Correlation Set
• Activities:• Basic Activities • Structured Activities (control flow)
Process Modelling and StandardizationFolie 28
BPEL4WS Example
flowsequence
sequence
sequence
Receive Purchase
Order
Reply Process Invoice
Price Calculation
Send Shipping Price
Receive Invoice
Assign Decide on Shipper
Receive Schedule
Initiate Production Scheduling
Complete Prod . Scheduling
receive invoke reply assign link
Andrews et al.: BPEL4WS 1.1., 2003
Process Modelling and StandardizationFolie 29
BPEL4WS Example
flow
Receive Purchase
Order
Reply Process Invoice
Price Calculation
Send Shipping Price
Receive Invoice
Assign Decide on Shipper
Receive Schedule
Initiate Production Scheduling
Complete Prod . Scheduling
Andrews et al.: BPEL4WS 1.1., 2003
Process Modelling and StandardizationFolie 30
Control Flow Problems
• Deadlock Freedomthere is no situation where a process instance has not yet reached a correct final state, but no activity can be finished anymore
• TerminatationThe flow must terminate exactly once without any residual branch being still under execution
• ReachabilityEach activity should be reachable – starting from a correct initial state there must be a valid sequence of activity executions and outputs that will lead to activation of X.
Reichert et al., 2004
Process Modelling and StandardizationFolie 31
Conclusion
• These control flow problems can only be analyzed fora subset of all BPEL
• BPEL4WS processes without links grant good control flow
• Restrictions on links allows analysis
• For details see Reichert, Rinderle, Dadam: On the modeling of correct service flows with BPEL4WS, 2004.
Process Modelling and StandardizationFolie 32
Process Design and Implementation
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 33
Petri Nets
• Places to capture states of a process
• Transitions to capture state changes
• Arcs to capture control flow
• Tokens to capture current state
Process Modelling and StandardizationFolie 34
Petri Net Example
Receive Purchase
Order
Reply Process Invoice
Price Calculation
Send Shipping Price
Receive Invoice
Assign Decide on Shipper
Receive Schedule
Initiate Production Scheduling
Complete Prod . Scheduling
i o
Process Modelling and StandardizationFolie 35
Soundness of Workflow Nets
Workflow Nets are special Petri Nets
Soundness implies:
• For every state M reachable from state I, there exists a firing sequence leading from state M to state o.
• State o is the only state reachable from state I with at least one token in place o.
• There are no dead transitions.
• For details see e.g. van der Aalst, 2000
Process Modelling and StandardizationFolie 36
Conclusion
• Rich mathematical foundations permits in-depth analysis
• Petri Nets are popular in academia
• There are several workflow engines that use Petri Nets
Process Modelling and StandardizationFolie 37
Process Design and Implementation
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 38
XPDL Concepts
• Standard proposed by Workflow Management Coalition
• Used in open source workflow engine OBE
• Workflow defined by activities and transitions
• Participants, applications, and data fields involved
Process Modelling and StandardizationFolie 39
XPDL Example
Allocate user ID
Create EMail
Account
Enter salary details
t3
<WorkflowProcesses> <WorkflowProcess AccessLevel="PUBLIC" Id="new-employee" Name="New Employee"> <Activities> <Activity Id="a5" Name="Allocate user ID"> <Implementation> <Tool Id="createNetworkUser" Type="PROCEDURE"> <ActualParameters> ... </ActualParameters> </Tool> </Implementation> <Performer>IT</Performer> <StartMode><Automatic/></StartMode> <FinishMode><Automatic/></FinishMode> <TransitionRestrictions> <TransitionRestriction> <Split Type="AND"> <TransitionRefs> <TransitionRef Id="t3"/> <TransitionRef Id="t4"/> <TransitionRef Id="t13"/> <TransitionRef Id="t25"/> <TransitionRef Id="t18"/> </TransitionRefs> </Split> </TransitionRestriction> </TransitionRestrictions> </Activity> ... </Activities> <Transitions> <Transition From="a5" Id="t3" Name="Transition" To="a6"/> ...
Grant access rights
t4
Assign phone
extension
t13
Configure computer
t18
t25
a5
a6
a8
a7
a4
a9
Process Modelling and StandardizationFolie 40
XPDL Schema Problems
• Missing Default values
• Undefined semantics
• Schema errors and ambiguities
• Schema omissions and inconsistencies
• For details, see Mendling, zur Muehlen, Price: Standards for Workflow Definition and Execution, in: Process-Aware Information Systems, 2005.
Process Modelling and StandardizationFolie 41
Conclusion
• XPDL in its current version needs rework
• Formal analysis is difficult, because of transition conditions
• Yet, some open source workflow engines use XPDL
Process Modelling and StandardizationFolie 42
Process Design and Implementation
Modelling Languages for Business Processes and Workflow
Process Implementation
Process Design
Event-Driven Process Chains (EPC)
BPEL4WS Petri Nets XPDL
Process Modelling and StandardizationFolie 43
Workflow Patterns
• Identification of control flow concepts
• List of 20 Workflow Patterns
• Generalization from EPCs, Petri Nets, etc.
• For details see van der Aalst et al., 2003
Process Modelling and StandardizationFolie 45
Business Process Lifecycle
Process Metrics
other reportingpurposes
ProcessImplementation
ProcessDesign
Process Enactment
Process Evaluation
Process Models
Impl
emen
ted
Pro
cess
es
Mea
sure
s fo
r Im
prov
emen
t
Process Metrics
Mea
sure
-men
ts
Process Monitoring
Animation,Simulation
Metrics,Targets
Goals,Evironmental
Analysis,Organizational
Analysis
Targ
et V
alue
s
M. zur Muehlen: Workflow-basedProcess Controlling, 2004
Process Modelling and StandardizationFolie 46
Overall Conclusion
• Heterogeneity is still a problem
• Standard proposals are often vendor driven
• Analysis of semantics is an important issue
• Workflow Patterns will hopefully be reflected in future standards