The document introduces BPMN, BPEL, and XPDL standards and proposes a new approach called BPeX. It analyzes weaknesses in XPDL like complex conceptual model, lack of referential integrity, and complex queries. BPeX aims to overcome these by having a clear conceptual model, strong referential integrity constraints, and allowing simple queries. A comparison shows BPeX has more expressive power and better support for analyses than XPDL.

1. Welcome
Michele Chinosi
University of Insubria – Varese (Italy)
BPeX: A New Approach to BPMN Model
Portability

2. Agenda
• Brief introduction to BPMN, WS-BPEL, XPDL
• BPeX: a new modeling approach
• A view of XPDL “weaknesses”
• How BPeX can aid to overcome these weak
points
• A comparison between XPDL and BPeX
April 21-23, 2008
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3. A Brief Introduction
• BPMN (Business Process Modeling Notation),
developed by BPMI and adopted as standard
by OMG (2006, BPMN 1.0 – 2008, BPMN 1.1)
• WS-BPEL (Web Services – Business Process
Execution Language), developed by BEA, IBM
& Microsoft, adopted by OASIS as standard.
Version 2.0 (2007).
• XPDL (XML Process Definition Language),
developed by WfMC. (2005, XPDL 2.0 – 2008,
XPDL 2.1).
April 21-23, 2008
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4. A Brief Introduction
• BPMN is a graphical notation to model
(represent) business processes.
– Standard for the look of a process
• WS-BPEL is an “execution language”
– definition of web services orchestration
– independent from BPMN
• XPDL stores and exchanges the process
diagrams
– process design format
– extended to support BPMN
April 21-23, 2008
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5. BPeX: Business Process eXtensions
The BPMN-XPDL-BPEL value chain
From Keith Swenson blog “Go Flow”, posted May 26, 2006
April 21-23, 2008
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6. BPeX: Business Process eXtensions
April 21-23, 2008
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7. A Comparison Between
WS-BPEL and XPDL
WS-BPEL XPDL
Expressive power Less expressive More expressive
Naming convention Completely different Some names different
Structure of the model Completely different Some relevant differences
Native referential integrity Partially Missing
Execution capabilities Full support No execution allowed
Graphical information Not at all Full graphical support
Validation / Analysis Complex queries Complex queries
April 21-23, 2008
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8. Some XPDL Weaknesses in
Details
• Elements renaming
• Complex conceptual model
• Lack of a native referential
integrity
• Complex queries
April 21-23, 2008
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9. Elements Renaming
XPDL 2.0:
•comes 1 year before OMG published BPMN specification
•supports all the elements provided by BPMN specification
•maintains the possibility to describe more generic workflow
diagrams
•avoid redundancy and duplicates
BPMN XPDL
Process WorkflowProcess
SequenceFlow Transition
SubProcess SubFlow
Gateway Route / Join / Split / …
April 21-23, 2008
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10. A Complex Conceptual Model
• We analyzed the XML serialization
provided with the example inside the XPDL
specification
• We depicted a more high-level graphical
conceptual model of the XML tree
• We compared the model with the Business
Process Diagram
April 21-23, 2008
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11. An Example Process
This process is taken from XPDL specification [Document
nr. WFMC-TC-1025, Section 8.1, pp. 109-127] and
modeled using BPMN
April 21-23, 2008
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12. A Complex Conceptual Model
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13. A Complex Conceptual Model
• XPDL was not originally developed to represent natively
BPMN diagrams
• XPDL has to maintain a backward compatibility with its
previous version
– Old names, old structure, old relationships
This introduces:
– more complexity
– some misunderstandings
– fragmentation of information
April 21-23, 2008
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14. A Complex Conceptual Model
BPMN XPDL
Processes are children of Pools Pools are defined separately from
elements WorkflowProcesses, referencing
them through relationships
Tasks are specifications of Activity Tasks are children of an
elements Implementation element,
descendant of an Activity block
which belongs to a unique Activities
element
Events are directly referenced from Events are children of an Activity
a Lane element element
One Gateway is defined within a The Route element is defined as
Lane child of an Activity
April 21-23, 2008
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15. Lack of Native Referential Integrity
Constraints
• All the elements do not have a unique ID
• ID and IDRef are of type xsd:NMTOKEN
• More than one element have the same ID
• BPMN specification requires the ID field to be
“a unique Id that identifies the object from
other objects within the Diagram”
April 21-23, 2008
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16. Lack of Native Referential Integrity
Constraints
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17. Lack of Native Referential Integrity
Constraints
• IDREFs are of type xsd:NMTOKEN
• It is possible to set as IDREF value a non-
existent ID
• There is the need of a software tool to check
the correctness of the values
• XPDL specification state that “The Process
attribute defines the Process that is contained
within the Pool”
April 21-23, 2008
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18. Lack of Native Referential Integrity
Constraints
April 21-23, 2008
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19. BPeX: Business Process
eXtensions
• ID and IDREF are defined as of types xsd:ID
and xsd:IDREF
• We add xsd:KEY and xsd:KEYREF to enforce
constraints
– We can assure that a Start Event of type
Message will have all and only the attributes
provided by BPMN specification
• We can statically validate the model without
using software tools
April 21-23, 2008
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20. Complex Queries
Which Lane does the Task with Id=10 belong to?
With XPDL
for $x in (//Activity[@Id=10]),
$y in (//Pool[@Process =
//$x/ancestor::WorkflowProcess[1]/@Id]//Lane/@Name)
return $y
Result:
/Package[1]/Pools[1]/Pool[2]/Lanes[1]/Lane[1]/@Name - Lane-0
With BPeX
//Lane[//Task/@Id=10]/@Name
Result:
/BPD[1]/Pool[2]/Lane[1]/@Name – Lane-0
April 21-23, 2008
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21. BPeX: Business Process
eXtensions
• Built from scratch with a clear conceptual model
• Not based on WS-BPEL or XPDL
– BPeX can be translated to XPDL and BPEL using XSLT
– BPeX can be extended to integrate XPDL or BPEL features
• It supports all BPMN elements and features
• It has an XML-Schema serialization
• It strengthens BPMN weak connections
• Static analysis and validation
• Constraints / Metrics / Extensions
April 21-23, 2008
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22. BPeX: success stories
• Partnership with Euranet (an European business consulting
company) and Università degli Studi di Bologna (Italy)
• We modeled some real cases taken from several SME
• We started implementing some constraints taken from NIST /
ISO procedures to aid users modeling processes
• We extended BPeX to support some simple time/cost metrics
(BPM 2007)
• We successfully added privacy policies to web-based
processes modeled with BPMN (WOSIS 2008)
April 21-23, 2008
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23. BPeX Conceptual Model
Graphical BPMN model
Graphical BPeX model
April 21-23, 2008
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24. Example Process in BPeX
April 21-23, 2008
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25. XPDL and BPeX comparison
XPDL
BPeX
April 21-23, 2008
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26. Conclusions
XPDL BPeX
Expressive power More expressive Bijective
correspondence
Naming convention Some names different No differences
Structure of the model Some relevant differences Few adjustments due
Native referential integrity Missing Strong
Execution capabilities No execution allowed Not yet but planned
Graphical information Full graphical support Supported with extensions
Analyses Complex queries required Simple queries
April 21-23, 2008
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27. Summary
• Introduction to BPMN, BPEL, XPDL
• Our proposal BPeX
• Analysis of the XPDL weak points using a
practical example
• How BPeX can aid to overcome these weak
points
• A comparison between XPDL and BPeX
April 21-23, 2008
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28. Questions?
michele.chinosi@uninsubria.it
http://bpex.sourceforge.net
April 21-23, 2008
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