1. Chapter 2 The Language: Rationale and Fundamentals (Part II)
Nick Russell
Arthur ter Hofstede

2. Outline Part II The BPM Landscape Conceptual Foundations
the Workflow Patterns Initiative
Control-flow patterns

3. Business Process Management (BPM)
“Supporting business processes using methods, techniques, and software to design, enact, control, and analyze operational processes involving humans, organizations, applications, documents and other sources of information”
W.M.P. van der Aalst, A.H.M. ter Hofstede, and M. Weske. Business Process Management: A Survey. In W.M.P. van der Aalst, A.H.M. ter Hofstede, and M. Weske, editors, International Conference on Business Process Management (BPM 2003), volume 2678 of Lecture Notes in Computer Science, pages 1–12. Springer-Verlag, Berlin, 2003.

4. Setting the scene – BPM: what and why?
Genesis in the fields of office information systems and workflow technology
Support for coordination of humans and applications in performing business activities
Explicit representation of control flow and data dependencies, and resourcing strategies
Benefits:
Improved efficiency (time, cost)
Compliance
Improved responsiveness

5. Evolution of BPM technology
Application
Application
Client Device
Client Device
Client Device
User Interface
User Interface
User Interface
User Interface
User Interface
Application
Application
Application
Application Logic
Application Logic
Application Logic
Application Logic
Service
Service
Service
Business Rules
Business Rules
Business Rules
Business Rules
Rules Engine
Control Flow
Control Flow
Control Flow
Business Rules
Data
Workflow
BPMS
Control Flow
Control Flow
Resourcing
Resourcing
Database System
Database System
Database System
Database System
Data
Data
Data
Data
1960s
1970s
1980s
1990s
2000s

6. Gartner top 10 strategic technologies 2008
Green IT
Unified communications
Business process modeling
Metadata management
Virtualization 2.0
Mashup & composite apps
Web platform & WOA (software as a service)
Computing fabric
Real world web
Social software     

7. BPM tools in active use by practitioners
BPTrends, The State of Business
Process Management 2008

8. Scope of BPMS offerings
M. Dumas, W.M.P van der Aalst, A.H.M ter Hofstede, Process-Aware Information Systems: Bridging People and Software through Process Technology, John Wiley & Sons, 2005

9. The BPM lifecycle Business Process Modelling Tools diagnosis process
design
Project
Management
Tools
process
enactment
Workflow
Management
Systems
process
implementation
M. Dumas, W. van der Aalst, A. ter Hofstede, Process-Aware Information Systems: Bridging People and Software through Process Technology, John Wiley & Sons, 2005

10. Problems in the BPM field
Lack of commonly accepted conceptual foundations
Lack of proper formal foundations (despite the rhetoric …)
No lack of proposed standards …
Tools are typically hard to use, expensive and not easily integrated
Lack of support for processes that need to change on-the-fly
Lack of proper support for exceptions
Limited support for design time analysis (verification and validation)
Resource perspective does not match real-world needs
Insufficient support for inter-process communication

11. Workflow animation
© Wil van der Aalst, Vincent Almering and Herman Wijbenga

12. Lack of commonly accepted conceptual foundations
How do various workflow environments deal with this? A B C D OR
AND
Forbid
Execute D once, ignore second triggering
Execute D twice
Execute D once or twice depending on execution …
SAP workflow ?
HP Change Engine
Werve, Forte conductor (numera uppköpt av SUN)
Staffware

13. BPMN: handling of concurrent execution threads

14. Staffware: handling of concurrent execution threads

15. Workflow Patterns Initiative
Started in 1999, joint work TU/e and QUT
Objectives:
Identification of workflow modelling scenarios and solutions
Benchmarking
Commercial BPM products (MQ/Series Workflow, Staffware, etc)
Open source workflow products (OpenWFE, jBPM, Enhydra Shark)
Proposed standards for web service composition (BPML, BPEL)
Process modelling languages (UML, BPMN)
Foundation for selecting workflow solutions
Home Page:
Primary publication:
W.M.P. van der Aalst, A.H.M. ter Hofstede, B. Kiepuszewski, A.P. Barros, “Workflow Patterns”, Distributed and Parallel Databases 14(3):5-51, 2003.
Citations: 1,500+ (Google Scholar); 500+ (Scopus); 300+ (Web of Science)
Evaluations of commercial offerings, research prototypes, proposed standards for web service composition, etc

16. Workflow Patterns Framework
Control-flow P:s 20
W. van der Aalst
A. ter Hofstede
B. Kiepuszewski
A. Barros
The ordering of
activities in a
process
2000
CoopIS’2000
DAPD’2003
2003
Jun 2005
Resource P:s - 43
Resource definition
& work distribution
in a process
N. Russell
W. van der Aalst
A. ter Hofstede
D. Edmond
CAiSE’2005
Oct 2005
Data P:s - 40
N. Russell
A. ter Hofstede
D. Edmond
W. van der Aalst
Data representation
and handling in a
process
ER’2005
Control-flow P:s 43
- 23 new patterns
Formalised in
CPN notation TR
N. Russell
A. ter Hofstede
W. van der Aalst
N. Mulyar
Sep 2006
revised
Exception P:s
Exception handling
in a process
CAiSE’2006
N. Russell
W. van der Aalst
A. ter Hofstede
Jun 2006
time
These perspectives follow S. Jablonski and C. Bussler’s classification from:
Workflow Management: Modeling Concepts, Architecture, and Implementation. International Thomson Computer Press, 1996

17. Workflow Patterns Framework
Control-flow P:s 20
2000
2003
XPDL, BPEL4WS, BPML,
WSFL, XLANG, WSCI,
UML AD 1.4 UML AD 2.0, BPMN
COSA
FLOWer
Eastman
Meteor
Mobile
I-Flow
Staffware
InConcert
Domino Workflow
Visual Workflow
Forte Conductor
MQSeries/Workflow
SAR R/3 Workflow Verve Workflow
Changengine
Jun 2005
Resource P:s - 43
BPEL4WS
UML AD 2.0
BPMN
Staffware
WebSphere MQ
FLOWer
COSA
iPlanet
XPDL, BPEL4WS
UML AD 2.0, BPMN
MQSeries
Data P:s - 40
Oct 2005
Exception P:s
Jun 2006
Staffware
WebSphere MQ
FLOWer
COSA
iPlanet
XPDL 2.0,
BPEL4WS 1.1, BPMN
Control-flow P:s 43
Sep 2006
revised
WebSphere I.D.
SAP
Filenet
Oracle BPEL
BPEL4WS, XPDL 2.0,
UML AD 2.0
BPMN, EPC (ARIS)
time
Eva l ua t I on s
Language Development: YAWL/newYAWL

18. Pattern validation: tool evaluation
Identify patterns
Set evaluation criteria
Select tools to be assessed
Assess pattern support
Review findings with vendors

19. Impact of the Workflow Patterns
Systems inspired or directly influenced by the patterns
FLOWer 3.0 of Pallas Athena Ivolutia Orchestration
Bizagi of Vision Software OpenWFE (an open source WFMS)
Staffware Process Suite Zebra (an open source WFMS)
Pectra Technology Inc.’s tool Alphaflow (an open source WFMS)
Lynx Workflow by InsuraPro jBPM (a free workflow engine)
Use of the workflow patterns in selecting a WFMS
the Dutch Employee Insurance Administration Office
the Dutch Justice Department
Other
Pattern-based evaluations (e.g. ULTRAflow, BPMN)
Main patterns papers are all highly cited
Education (used in teaching at 10+ Universities)
Web site: 300+ visits on an average working day

20. What is a pattern ?
“Abstraction from concrete form which keeps recurring in specific, non-arbitrary contexts”
D. Riehle and H. Züllighoven. Understanding and Using Patterns in Software Development. Theory and Practice of Object Systems 2(1):3-13, 1996.
In process context:
Imperative in format
Not dependent on actual
products/technologies
Motivated
Solution-oriented
Components
Description: what is it?
Synonym(s)
Example(s)
Motivation: why needed?
Context: conditions + CPN formalisation
Implementation: how typically realised?
Issues: what problems can be encountered?
Solutions: how and to what extent can these problems be overcome?
Evaluation criteria

21. Business process perspectives: ARIS (source: A. W
Business process perspectives: ARIS (source: A.W. Scheer, ARIS – Business Process Modelling, Springer, Berlin, Germany, 2000.)

22. Business process perspectives: CIMOSA (source: F. B
Business process perspectives: CIMOSA (source: F.B. Vernadat, Enterprise Modeling and Integration. Chapman and Hall, London, UK, 1996.)

23. Business process perspectives: Zachman Framework (source: J.A. Zachman. A framework for information systems architecture. IBM Systems Journal, 26(3): , 1987.)
Source:

24. Workflow perspectives: control-flow and data
Control-flow perspective
Focuses on the representation and execution of processes in terms of tasks and arcs indicating how the thread of control is passed between them
Abstracts from the actual implementation of individual tasks
Data perspective
Focuses on the representation and utilisation of data in a process context
Considers both internal and external data resources and the interactions between them

25. Workflow perspectives: resource
Focuses on the manner in which work is offered to, allocated to and managed by process participants
Considers both the system and resource perspectives
Assumes the existence of a process model and related organisational and work distribution models
Takes into account differing operational paradigms:
richness of process model (esp. allocation directives)
autonomy of resources
alternate routing mechanisms
work management facilities

26. Control-flow patterns overview

27. Classes of control-flow patterns
Branching Patterns capture branching scenarios in processes.
Synchronisation Patterns describe synchronization scenarios arising in processes.
Repetition Patterns describe various ways in which repetition may be specified.
Multiple Instances (MI) Patterns delineate situations with multiple threads of execution in a workflow which relate to the same activity.
Concurrency Patterns
reflect situations where restrictions are imposed on the extent of concurrent control-flow in a process instance
Trigger Patterns
catalogue the different triggering mechanisms appearing in a process context.
Cancellation and Completion Patterns
categorise the various cancellation scenarios that may be relevant for a workflow specification.
Termination Patterns
address the issue of when the execution of a workflow is considered to be finished.

28. Branching constructs AND Split
Parallel split, initiation of parallel threads
OR Split
Multi-choice, thread of control is passed to one or more outgoing branches
XOR Split
Exclusive choice, thread of control is passed to exactly one of the outgoing branches
Deferred choice, thread of control is passed to exactly one of the outgoing branches. Selection decision is deferred to the user and/or operating environment.
Thread Split
Thread split, thread of control is split into multiple concurrent threads in same branch.

29. Branching patterns Parallel split, initiation of parallel threads
Multi-choice, thread of control is passed to one or more outgoing branches
Exclusive choice, thread of control is passed to exactly one of the outgoing branches
Deferred choice, thread of control is passed to exactly one of the outgoing branches. Selection decision is deferred to the user and/or operating environment.
Thread split, thread of control is split into multiple concurrent threads in same branch.

30. Parallel split Definition CPN:
The divergence of a branch into two or more parallel branches each of which execute concurrently.
Definition CPN:

31. Multi-choice
The divergence of a branch into two or more branches such that when the incoming branch is enabled, the thread of control is immediately passed to one or more of the outgoing branches based on a mechanism that selects one or more outgoing branches.
Definition CPN:
context condition: choice construct has access to all required resources when making routing decision

32. Multi-choice
Straightforward when transition conditions are supported (e.g. MQSeries/Workflow, Verve, Forte Conductor).
Otherwise:
and-split followed by xor-splits exhausting all combinations;
xor-split followed by and-splits (only needed if combination contains more than one branch) exhausting all combinations.

33. Multi-choice: Example (source: [AHKB03] p.14)
y>7
Solution 1: A A
Solution 2:
AND
x<5 & y>7
XOR
x5 & y7
AND
XOR
XOR
x<5 & y7
x<5
y>7
y7 B C B B
x5 C
x5 & y>7 C

34. Deferred choice Choice made by the environment not the system
Essential in workflow context
Not widely supported, though its importance seems to be increasingly recognised (e.g. BPEL)
Naturally supported by notations that offer direct support for the notion of state, e.g. statecharts or Petri nets
vs WCP 4 Exclusive Choice
Choice made by the system, based on data

35. Deferred choice vs Exclusive choice: definitions
context condition: only one instance of the construct can operate at any time in a case
Exclusive choice
context condition: choice construct has access to all required resources when making routing decision
+ FLOWer, COSA, BPEL, Oracle BPEL, BPMN, XPDL, UML 2.0 AD
- EPC (implemented by ARIS toolset 6,2, SAP Workflow 4.6c, iPlanet 3.0, Staffware 10, WebSphere MQ 3.4

36. Deferred choice vs Exclusive choice
+ FLOWer, COSA, BPEL, Oracle BPEL, BPMN, XPDL, UML 2.0 AD
- EPC (implemented by ARIS toolset 6,2, SAP Workflow 4.6c, iPlanet 3.0, Staffware 10, WebSphere MQ 3.4

37. Deferred Choice - UML
Solution in UML 2.0 AD

38. Deferred choice - BPMN Solution in BPMN
with Event-Based Exclusive Gateway
and Message Events
with Event-Based Exclusive Gateway
and Receive Activities

39. Thread split
At a given point in a process, a nominated number of execution threads can be initiated in a single branch of the same process instance.
Definition CPN
context condition: required number of threads known at design-time

40. Synchronisation patterns: AND-join variants
Synchronisation, wait for all incoming threads
context assumption: each incoming branch will signal exactly once
Generalised AND-Join, wait for all incoming threads
Structured partial join, wait for some (but not all) incoming threads
context assumption: structured workflow
Blocking partial join, wait for some (but not all) incoming threads
context assumptions: workflow is safe, join blocks until remaining threads arrive
Cancelling partial join, wait for some incoming threads, cancel the rest

41. Synchronisation patterns: the differences

42. Synchronisation vs Generalised AND-Join
Definition CPN
Context condition (Synchronisation) Once the synchroniser has been activated (and not reset), it is not possible for another signal to be received on the activated branch or for multiple signals to be received on
any incoming branch.

43. Structured partial join
Triggered by completion of n of the m parallel incoming branches (where n < m)
Subsequent threads do not cause triggering
Partial join resets when all branches have completed
Context conditions
Corresponding and-split
All branches structured (e.g. balanced corresponding splits and joins)
Either all branches can be cancelled or none
Special case where n=1 is sometimes termed the discriminator

44. Structured partial join

45. Structured partial join: operation
- UML 2.0 AD, SAP Workflow 4.6c, iPlanet 3.0, COSA 5.1, Staffware 10
+ Webshpere MQ 3.4, FLOWer 3.51, FileNet 3.5, BPEL 1.1, Oracle BPEL , BPMN 1.0, XPDL 2.0, EPC (as implemented in Aris toolset 6.2)

46. Structured partial join: CPN definition
- UML 2.0 AD, SAP Workflow 4.6c, iPlanet 3.0, COSA 5.1, Staffware 10
+ Webshpere MQ 3.4, FLOWer 3.51, FileNet 3.5, BPEL 1.1, Oracle BPEL , BPMN 1.0, XPDL 2.0, EPC (as implemented in Aris toolset 6.2)

47. Structured partial join: Usage issue
Structured workflow
imposes serious
usage restrictions
blocking and
cancelling pattern
variants
- UML 2.0 AD, SAP Workflow 4.6c, iPlanet 3.0, COSA 5.1, Staffware 10
+ Webshpere MQ 3.4, FLOWer 3.51, FileNet 3.5, BPEL 1.1, Oracle BPEL , BPMN 1.0, XPDL 2.0, EPC (as implemented in Aris toolset 6.2)

48. Blocking partial join
Removes the requirement that each incoming branch can only be enabled once between join resets.
It allows each incoming branch to be triggered multiple times although the construct only resets when one triggering has been received on each input branch

49. Cancelling partial join
Improves the efficiency of the pattern further by cancelling the other incoming branches to the join construct once n incoming branches have completed

50. Synchronisation patterns: OR-join variants
Structured synchronising merge, wait for all enabled branches
context assumptions: structured workflow, local semantics
Local synchronising merge, wait for all enabled branches
context assumption: local semantics
General synchronising merge, wait for all enabled branches

51. Structured synchronising merge: operation
Structured synchronising merge, wait for all enabled branches
context assumptions: structured workflow, local semantics
- UML 2.0 AD, SAP Workflow 4.6c, iPlanet 3.0, COSA 5.1, Staffware 10
+ Webshpere MQ 3.4, FLOWer 3.51, FileNet 3.5, BPEL 1.1, Oracle BPEL , BPMN 1.0, XPDL 2.0, EPC (as implemented in Aris toolset 6.2)

52. Structured synchronising merge
Convergence of two or more branches (which diverged earlier in the flow) into a single subsequent branch. The thread of control is passed to the subsequent branch when each active incoming branch has been enabled.
Context conditions:
Single earlier corresponding multi-choice
While merge has not fired, this multi-choice cannot be re-enabled
No cancellation of selective branches after firing multi-choice
These conditions are such that firing decision can be made based on local knowledge

53. Structured synchronising merge

54. Structured synchronising merge: possible realisations I

55. Structured synchronising merge: possible realisations II

56. Local synchronising merge
This pattern does not require the process model to be structured, but its usage in the context of loops is restricted
A possible realisation is through so-called “dead-path elimination” (see MQSeries, BPEL – note the implication this has on the types of loops allowed)
Evaluation of whether this merge is enabled can still be done locally

57. Local synchronising merge: CPN definition

58. Local synchronising merge: another solution
Communication between OR-split and OR-join
cf. Rittgen, 1990
active
branches A OR
split OR
join Z

59. Local synchronising merge: operation
WebSphere MQ, FLOWer, COSA, BPEL and EPCs provide support for this pattern. UML 2.0 ADs seems to provide support although there is some ambiguity over the actual JoinSpec configuration required
context conditions: (1) all input places to the construct are
(2) must be able to determine how many incoming
branches to synchronise based on local knowledge

60. A (very) complex CF pattern: General synchronising merge
Basically: Wait only if you have to
Problems:
How should you treat other OR-joins?
How do you deal with cycles?
How do you treat decomposed tasks?
Is an analysis of the future possible? How complex will it be?
(for a detailed discussion see [WEAH05] and work by Kindler et al)

61. Non-local semantics of General Synchronising Merge ("bus driver semantics")
Not only in EPCs but also in many WFM systems: Domino Workflow, Eastman, MQ Series, etc.

62. General Synchronising Merge in CPN

63. General synchronising merge: operation
FileNet 3.5 supports this pattern
context conditions: none!

64. Synchronisation patterns: XOR and thread join
XOR-join variants
Simple merge,wait for one of the incoming branches
context assumption: only one incoming branch active
Multi-merge, wait for one of the incoming branches
Thread join variants
Thread merge, coalesce specified number of threads in branch into single thread

65. XOR-join variants: Simple & Multi-merge
context condition: the merge construct will never receive another
execution thread whilst it is merging
a previously received thread onto the
output branch
context condition: the merge construct must be associated with a preceding multi-choice (OR-split)

66. BPMN
BPMN
Several solutions for the most basic patterns

67. Basic control-flow patterns in UML2.0 AD

68. Repetition patterns - 1
Structured loop, the ability to execute a task or sub-process repeatedly on the basis of a pre or post test where there is a single entry/exit point

69. Repetition patterns - 2
Describe various ways in which repetition of tasks or sub-processes may be specified.
Arbitrary cycles, cycles in a process with more than one entry or exit point
Recursion, repetition of a task through self-invocation

70. Arbitrary Cycles & Expressiveness
Not all arbitrary cycles can be converted into structured ones (e.g. while or repeat loops; for further details see [KtHB00] and [Kie03]).
Block structured offerings such as WebSphere MQ, FLOWer, SAP Workflow and BPEL are not able to represent arbitrary process structures.

71. Multiple instance patterns
Delineate situations with multiple threads of execution in a workflow
which relate to the same activity
MI without Synchronisation, multiple concurrent instances but no synchronisation requirements
MI with a priori Design Time Knowledge, number of concurrent instances known at design-time, all must finish
MI with a priori Runtime Knowledge, number of concurrent instances known at runtime, all must finish
MI without a priori Runtime Knowledge, number of concurrent instances only known at completion, all must finish
Static Partial Join for MI, number of concurrent instances known at design-time, specified number must finish, remainder inconsequential
Cancelling Partial Join for MI, number of concurrent instances known at design-time, specified number must finish, remainder cancelled
Dynamic Partial Join for MI, number of concurrent instances only known at completion, dynamic completion condition

72. MI patterns: variation points

73. MI without synchronisation
context condition: the number of task instances is fixed at design-time

74. MI without synchronisation in CPN

75. Multiple instances without synchronisation (source: [AHKB03], p. 24)

76. MI without Synchronization
Solution in UML 2.0 AD
Solution in BPMN

77. MI with a priori runtime knowledge
context condition: the number of task instances is fixed at design-time

78. MI with a priori runtime knowledge in CPN

79. Multiple instances with a priori runtime knowledge (source: [AHKB03], p. 24)

80. Multiple instances with a priori runtime knowledge (source: [AHKB03], p. 24)

81. MI with a Priori Run-Time Knowledge
Solution in UML 2.0 AD
Solution in BPMN

82. MI without a Priori Run-Time Knowledge
Creation of a number of concurrently executing instances of an activity, this number is not known before invocation of the MI activity. Synchronisation of all instances created is required.
More advanced MI patterns address:
Creation of new instances on-the-fly
Threshold for completion (partial join)
Cancellation of remaining threads in case of a partial join

83. MI without a Priori Run-Time Knowledge: Definition

84. MI without a Priori Run-Time Knowledge: Animation

85. Multiple instances without a priori runtime knowledge (source: [AHKB03], p. 28)

86. MI without a Priori Run-Time Knowledge
Workaround in UML 2.0 AD
NB! In practice this pattern is implemented by the user.
Solution with object streams and weights
The solutions require advanced
data manipulation and
special attribute settings.
Solution with variables

87. MI without a Priori Run-Time Knowledge
Workaround in BPMN
NB! In practice, a modeller has to implement this pattern.
The solution requires advanced data manipulation and special attribute settings.

88. Dynamic partial join for MI: operation

89. Dynamic partial join for MI
context conditions:
initial number of instances is set at design-time
must be possible to evaluate completion condition

90. Concurrency patterns
Reflect situations where restrictions are imposed on the extent of concurrent control-flow in a process instance
Sequence, sequential task execution
Interleaved routing, execution of a set of tasks can occur in any order but not concurrently
Interleaved parallel routing, a set of tasks, which have a partial ordering amongst them, and execute in order order that satisfies this sequence but not concurrently
Critical section, two or more regions in a process model that cannot be active simultaneously
Milestone, the execution of a nominated task can only proceed when the process instance is in a specified state

91. Sequence Definition CPN:
An activity in a workflow process is enabled after the completion of a preceding activity in the same process.
Definition CPN:

92. Interleaved routing: operation
Interleaved routing, execution of a set of tasks can occur in any order but not concurrently

93. Interleaved routing: definition
context condition: tasks initiated and completed sequentially and cannot be suspended

94. Milestone
In some cases a thread needs to check whether some other parallel thread has reached a certain point (but has not moved beyond it)
As long as this is the case a certain task may execute
Hard to realise when a language does not support the notion of state explicitly

95. Milestone (source: [AHKB03], p. 36)

96. Milestone (source: [AHKB03], p. 35)

97. Milestone
The execution of a nominated task can only proceed when the process instance is in a specified state

98. Milestone in CPN

99. Trigger patterns
Allow for synchronisation with the operating environment
Persistent trigger, task initiation triggered by external signal. Triggers are durable and retained if not immediately used
Transient trigger, task initiation triggered by external signal. Triggers are emphemeral and are lost if not immediately used

100. Cancellation and completion patterns
Categorise the various cancellation scenarios that may be
relevant for a workflow specification
Cancel task, withdraw a specified task instance
Cancel case, withdraw all task instances in a case
Cancel region, withdraw task instances in a specified region of a process
Cancel MI task, withdraw all instances of a specified MI task
Complete MI task, withdraw all remaining instances of a specified MI task, completed instances are unaffected and the MI task is deemed to have sucessfully completed

101. Cancellation region Generalisation of Cancel activity and Cancel case
Region associated with a task
This region is emptied of tokens upon completion of that task.
Rarely fully supported (only UML 2.0 ADs through InterruptibleActivityRegion construct and YAWL)

102. Cancel region pattern

103. Cancel region: operation

104. Termination patterns Address the issue of when the execution of a
workflow is considered to be finished
Implicit termination, finish the case when there is no more work to do
Explicit termination, finish the case when the thread of control reaches a specified end node

105. UML activity diagram - 1 What are the termination semantics?
ActivityFinalNode
What are the termination semantics?
→ explicit termination

106. UML activity diagram - 2 FlowFinalNode
What are the termination semantics?
→ implicit termination

107. UML activity diagram - 3
What are the termination semantics?

108. BPMN – termination semantics 1
→ implicit termination
End Event
End Event

109. BPMN – termination semantics 2
→ explicit termination
Terminate
End Event
Terminate
End Event

110. Control-flow perspective: evaluation
1 – BPMN 2 – UML AD 3 – BPEL

111. Epilogue - I
Patterns
Provide an effective foundation for training workflow designers and developers;
Present a means of assessing and comparing tool capabilities and are particularly useful in tool evaluation and selection exercises (e.g. tender evaluations);
Offer the basis for vendors to identify functionality gaps and potential areas for enhancement.

112. Epilogue - II Patterns range from simple to (very) complex
Patterns typically observed
Comprehensive support lacking
Problems so complex that informal approaches fall short

113. Further details Key papers Online references www.workflowpatterns.com
W.M.P van der Aalst, A.H.M. ter Hofstede, B. Kiepuszewski, and A.P. Barros. Workflow Patterns. Distributed and Parallel Databases, 14(3), pages 5-51, July 2003.
N. Russell, A.H.M. ter Hofstede, W.M.P. van der Aalst, and N. Mulyar. Workflow Control-Flow Patterns: A Revised View. BPM Center Report BPM-06-22, BPMcenter.org, 2006.
Online references

114. Instruction questions - 1
Sketch the Petri-net representations of the main control-flow connectors i.e.
AND-split
OR-split
XOR-split
AND-join
OR-join
XOR-join
Each of these constructs can be represented by a number of distinct control-flow patterns. What are the correspondences between these constructs and the various control-flow patterns?
What are the difficulties associated with the use of the OR-join construct?

115. Instruction questions - 2
Identify the control-flow patterns in the following process model

116. Instruction questions - 3
Model the following process as a YAWL process model
A travel agency makes travel arrangements for people
A travel arrangement may include one or more of the following activities: book flight, book car and book hotel
These activities occur in parallel
As they involve dealing with third parties, each of the booking activities may be either successful or unsuccessful
When all booking activities requested by a customer have completed successfully, the payment activity is triggered
If any of the booking activities are unsuccessful, any further progress on the booking activities (if any) is cancelled
The process completes after either a payment or cancellation activity
What difficulties arise when trying to model this as a Petri net?

117. Instruction questions - 4
Illustrate how the cancel case pattern could be applied to a process model

118. Instruction questions - 5
The illustration below shows the nominal form of the milestone pattern. The difficulty with this form is that if the thread of control has passed place X, then the milestone task will never be enabled. Modify the model so that the milestone task can still be enabled if the thread of control has already passed X.

119. Instruction questions - 6
Sketch the Petri-net representations for the following situations. Which pattern do each of them correspond to?
After the sound alarm task, either the evacuate lab task or the handle false alarm task commences depending on whether the value of the heat sensor variable is above 30 degrees
At the conclusion of the test oil pressure, the pilot decides to initiate the repressure task or ignore reading and reset task depending on the oil pressure returned
When the calculate depth task completes, based on the value returned for the depth, if it is less than 5 metres, initiate the short fill task, it is is greater than 5 metres initiate the long fill task, if it is greater than 10 metres initiate the check valve task
Run the g23 genome sequence task, then run the g24 genome sequence and/or the g25 genome sequence task
Run the measure yeast content task, after this has completed if the time is before 12:00pm, run the fill main tank task otherwise run the fill task 2 task

120. Instruction questions - 7
Outline the possible approaches to implementing a 1-out-of-3 join. What are the advantages and disadvantages of each?
The Ad-hoc activity construct in BPMN allows a set of nominated tasks to run in arbitrary order. Each task can execute an arbitrary number of times (including not at all). Draw the Petri-net to illustrate the behaviour of this construct where it contains four tasks A, B, C and D. How does this behaviour compare to the interleaved routing patterns?

121. Instruction questions - 8
The local synchronising merge relies on local semantics for its operation i.e., the OR-join must be able to determine when to fire based on the availability of locally available information
Why might this approach to OR-join enablement be popular with tool vendors?
How might you implement this form of OR-join?
WebSphere MQ, FLOWer, COSA, BPEL and EPCs provide support for this pattern. UML 2.0 ADs seems to provide support although there is some ambiguity over the actual JoinSpec configuration required

122. References I www.workflowpatterns.com
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W.M.P. van der Aalst. Don't go with the flow: Web services composition standards exposed. Web Services - Been there done that?, Trends & Controversies. IEEE Intelligent Systems 18(1):72-76.
Wil M.P. van der Aalst and Kees M. van Hee. Workflow Management: Models, Methods, and Systems. The MIT Press, 2002.
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W.M.P. van der Aalst, M. Dumas, and A.H.M. ter Hofstede. Web Service Composition Languages: Old Wine in New Bottles? In G. Chroust and C. Hofer, editors, Proceedings of the 29th EUROMICRO Conference: New Waves in System Architecture, pages IEEE Computer Society, Los Alamitos, CA, 2003.
M. Dumas and A. ter Hofstede. UML Activity Diagrams as a Workflow Specification Language. In Proceedings of the International Conference on the Unified Modeling Language (UML), Toronto, Canada, October Springer Verlag.

123. References II
Marlon Dumas, Wil M.P. van der Aalst, Arthur H.M. ter Hofstede (Editors), Process-Aware Information Systems: Bridging People and Software Through Process Technology, John Wiley & Sons, September 2005.
B. Kiepuszewski, A.H.M. ter Hofstede, C. Bussler. On Structured Workflow Modelling. Proceedings CAiSE’2000, Lecture Notes in Computer Science 1789, Stockholm, Sweden, June 2000.
B. Kiepuszewski. Expressiveness and Suitability of Languages for Control Flow Modelling in Workflows. PhD thesis, Queensland University of Technology, Brisbane, Australia, 2003.
B. Kiepuszewski, A.H.M. ter Hofstede and W.M.P. van der Aalst. Fundamentals of Control Flow in Workflows. Acta Informatica 39(3): , 2003.
P. Rittgen. From process model to electronic business process. In D. Avison, E. Christiaanse, C.U. Ciborra, K. Kautz, J. Pries-Heje, and J. Valor, editors, Proceedings of the European Conference on Information Systems (ECIS 1999), pages 616–625, Copenhagen, Denmark,
N. Russell, A.H.M. ter Hofstede, W.M.P. van der Aalst, and N. Mulyar. Workflow Control-Flow Patterns: A Revised View. BPM Center Report BPM , BPMcenter.org, 2006.
N. Russell, Wil M.P. van der Aalst , A.H.M. ter Hofstede , and Petia Wohed. On the Suitability of UML 2.0 Activity Diagrams for Business Process Modelling. In M. Stumptner, S. Hartmann, and Y. Kiyoki, editors, Proceedings of the Third Asia-Pacific Conference on Conceptual Modelling (APCCM2006), volume 53 of CRPIT, pages , Hobart, Australia, ACS.

124. References III
P. Wohed, E. Perjons, M. Dumas, and A. ter Hofstede, Pattern-Based Analysis of EAI Languages: The Case of the Business Modeling Language. in Proc. of the 5th Int. Conf. on Enterprise Information Systems (ICEIS), Angers, France, April 2003.
P. Wohed, W.M.P. van der Aalst, M. Dumas, and A.H.M. ter Hofstede, Analysis of Web Services Composition Languages: The Case of BPEL4WS. in I.Y. Song, et al, eds, 22nd Int. Conf. on Conceptual Modeling (ER 2003), vol of LNCS, pp , Springer-Verlag, 2003.
P. Wohed, W.M.P. van der Aalst, M. Dumas, A.H.M. ter Hofstede, and N. Russell, Pattern-based Analysis of the Control-Flow Perspective of UML Activity Diagrams. in L. Delcambre et al., eds, Proc. of the 24th Int. Conf. on Conceptual Modeling (ER 2005), vol of LNCS, pp Springer-Verlag, Berlin, 2005.
P. Wohed, W.M.P. van der Aalst, M. Dumas, A.H.M. ter Hofstede, and N. Russell, On the Suitability of BPMN for Business Process Modelling. in Proc. of the 4th Int. Conf. on Business Process Management, Vienna, September 2006.
P. Wohed, W.M.P. van der Aalst, M. Dumas, A.H.M. ter Hofstede, and N. Russell. Pattern-based Analysis of BPMN - An extensive evaluation of the Control-flow, the Data and the Resource Perspectives (revised version) . BPM Center Report BPM , BPMcenter.org, 2006.
M. Wynn, D. Edmond, W.M.P. van der Aalst, A.H.M. ter Hofstede. Achieving a General, Formal and Decidable Approach to the OR-join in Workflow using Reset nets. Proceedings of ATPN’2005. Miami, Florida, 2005.

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