bpex: a new approach to bpmn model portability - updated version

Welcome

Michele ChinosiUniversity of Insubria – Varese (Italy)

BPeX: A New Approach to BPMN Model Portability

April 21-23, 2008 Renaissance Washington, DC

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

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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).



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



BPeX: Business Process eXtensions


The BPMN-XPDL-BPEL value chainFrom Keith Swenson blog “Go Flow”, posted May 26, 2006


A Comparison BetweenWS-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



Some XPDL Weaknesses in Details

• Elements renaming

• Complex conceptual model

• Lack of a native referential integrity

• Complex queries



Elements RenamingXPDL 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 / …


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



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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• 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




BPMN XPDL

Processes are children of Pools elements

Pools are defined separately from WorkflowProcesses, referencing them through relationships

Tasks are specifications of Activity elements

Tasks are children of an Implementation element, descendant of an Activity block which belongs to a unique Activities element

Events are directly referenced from a Lane element

Events are children of an Activity element

One Gateway is defined within a Lane

The Route element is defined as child of an Activity



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”




• 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”




• 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



Complex Queries

With XPDLfor $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


Which Lane does the Task with Id=10 belong to?


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



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)



BPeX Conceptual Model

Graphical BPMN model

Graphical BPeX model



Example Process in BPeX



XPDL and BPeX comparison


BPe

X XP

DL


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


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



[email protected]://bpex.sourceforge.net

28Michele Chinosi - Architecture & Process - 2008