bpex: a new approach to bpmn model portability

Welcome

Michele ChinosiUniversity of Insubria – Varese (Italy)

BPeX: A New Approach to BPMN Model Portability

April 21-23, 2008 Renaissance Washington, DC

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).

Michele Chinosi - Architecture & Process - 2008 2


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



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

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


April 21-23, 2008 Renaissance Washington, DCMichele Chinosi - Architecture & Process - 2008 11




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”



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?



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




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



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


[email protected]

http://bpex.sourceforge.net

25Michele Chinosi - Architecture & Process - 2008

bpex: a new approach to bpmn model portability

Business

renaissance washington

process attribute

business process diagramapril

bpmn xpdl stores

bpmn diagrams xpdl

complex conceptual model

bpmn model portability

xpdl weaknesses