Architecture+Processes Conference, Washington DC, April 2008, organized by WfMC

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

2. A Brief Introduction
BPMN (Business Process Modeling Notation),
developed by BPMI and adopted as standard
by OMG (2006).
WS-BPEL (Web Services – Business Process
Execution Language), developed by IBM &
Microsoft, adopted by OASIS as standard.
Version 2.0 (2007).
XPDL (XML Process Definition Language),
developed by WfMC. Version 2.0 (2005).
April 21-23, 2008
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3. A Brief Introduction
BPMN is a graphical notation to model
(represent) business processes
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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4. 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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5. BPeX: Business Process eXtensions
April 21-23, 2008
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6. 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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7. 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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8. 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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9. A Complex Conceptual Model
We analyzed the XML serialization
provided with the example
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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10. 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
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11. A Complex Conceptual Model
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12. 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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13. 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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14. 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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15. Lack of Native Referential Integrity
Constraints
April 21-23, 2008
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16. 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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17. Lack of Native Referential Integrity
Constraints
April 21-23, 2008
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18. 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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19. BPeX: Business Process
eXtensions
Built from scratch
Clear conceptual model
Not based on WS-BPEL or XPDL
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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20. 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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21. BPeX Conceptual Model
Graphical BPMN model
Graphical BPeX model
April 21-23, 2008
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22. Example Process in BPeX
April 21-23, 2008
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23. XPDL and BPeX comparison
XPDL
BPeX
April 21-23, 2008
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24. 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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25. Questions?
michele.chinosi@uninsubria.it
http://bpex.sourceforge.net
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