Pal gov.tutorial3.session13.bpel

‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps

Tutorial III:
Process Integration and Service Oriented Architectures

Session 13
BPEL

Prepared By

Mohammed Aldasht

PalGov © 2011 1

About

This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the
Commission of the European Communities, grant agreement 511159-TEMPUS-1-
2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )

Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium

Palestine Technical University, Palestine
Université de Savoie, France

Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine

Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

© Copyright Notes
Everyone is encouraged to use this material, or part of it, but should properly
cite the project (logo and website), and the author of that part.

No part of this tutorial may be reproduced or modified in any form or by any
means, without prior written permission from the project, who have the full
copyrights on the material.

Attribution-NonCommercial-ShareAlike
CC-BY-NC-SA

This license lets others remix, tweak, and build upon your work non-
commercially, as long as they credit you and license their new creations
under the identical terms.

PalGov © 2011 3

Tutorial Map

Intended Learning Objectives
A: Knowledge and Understanding
Title T Name
3a1: Demonstrate knowledge of the fundamentals of middleware.
3a2: Describe the concept behind web service protocols.
Session0: Syllabus and overview 0 Aldasht
3a3: Explain the concept of service oriented architecture. Sesson1: Introduction to SOA 2 Aldasht
3a4: Explain the concept of enterprise service bus. Session2: XML namespaces & XML schema 2 Aldasht
3a5: Understanding WSDL service interfaces in UDDI. Session 3: Xpath & Xquery 4 Romi
B: Intellectual Skills Session4: REST web services 3 M. Melhem
3b1: Design, develop, and deploy applications based on Service Session5: Lab2: Practice on REST 3 M. Melhem
Oriented Architecture (SOA). Session 6: SOAP 2 Aldasht
3b2: use Business Process Execution Language (BPEL). Session 7: WSDL 3 Aldasht
3b3: using WSDL to describe web services.
Session8: Lab 3: WSDL practice 3 Aldasht
C: Professional and Practical Skills Session9: ESB 4 Aldasht
3c1: setup, Invoke, and deploy web services using integrated
Session10: Lab4: Practice on ESB 4 Aldasht
development environment.
Session11: integration patterns 4 M. Melhem
3c2: construct and use REST and SOAP messages for web
services communication. Session12: Lab5: integration patterns 4 M. Melhem
D: General and Transferable Skills Session13: BPEL 3 Aldasht
d1: Working with team. Session14: Lab6: Practice on BPEL 2 Aldasht
d2: Presenting and defending ideas. Session15: UDDI 3 Aldasht
d3: Use of creativity and innovation in problem solving.
d4: Develop communication skills and logical reasoning abilities.

Session 13: Component based service
development/ WS composition (BPEL).

Session ILOs
After completing this module students will be
able to use business process execution
language BPEL.

PalGov © 2011 5

Session Outlines

 Introduction
 Partners
 BPEL: Important features
 BPEL for Service Composition
 Developing BP with BPEL
 BPEL process example

PalGov © 2011 6

Overview

BPEL4WS
WS-Transaction

UDDI
WSDL

SOAP
Relationship among standards, Source, [2]

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Introduction

• A business process specifies the potential
execution order of operations from [2]:
– A collection of web services
– The data shared between these web services
– Other issues involving which partners are involved,
how multiple services and organizations participate
• This especially allows:
– Specifying long-running transactions between web
services.
– Increasing consistency and reliability for web
services applications.
PalGov © 2011 8

Introduction, cont.

• To enable users to connect different
components even across organizational
boundaries in a platform- and language-
independent manner, standards used:
– WSDL to describe the Web service.
– UDDI to advertise and organize Web services.
– SOAP to communicate with Web service.

PalGov © 2011 9

Introduction, cont.

• BPEL allows specifying business processes
and how they relate to web services [2].
– Business processes specified in BPEL are fully
executable and portable.
– A BPEL business process interoperates with the
web services of its partners.
– BPEL supports the specification of business
protocols between partners.

PalGov © 2011 10

General structure of a BPEL for web
service process

<process ...>

<partners> ... </partners>

<containers> ... </containers>
<!– Data used by the process -->
<correlationSets> ... </correlationSets>
<!– Used to support asynchronous interactions -->
<faultHandlers> ... </faultHandlers>
<!–Alternate execution path to deal with faulty conditions -->
<compensationHandlers> ... </compensationHandlers>
<!–Code to execute when “undoing” an action -->
(activities)*
<!– What the process actually does -->

</process>

PalGov © 2011 11

Session Outlines

 Introduction
 Partners

PalGov © 2011 12

Partners

• The partners of business processes involving
web services often interact with.
• Partners are connected to a process in a
bilateral manner partner links [2].
• Process can use the partner link to speak to a
specific web service.

PalGov © 2011 13

Partners, cont.

• Partners are one of the following [1]:
– Services that the process invokes only.
– Services that invoke the process only.
– Or services that the process invokes and
invoke the process

PalGov © 2011 14

Automation of Business Processes

• For efficient automation of business processes
through IT we need to:
– Provide a standardized way to expose and access
the functionality of applications as services.
– Provide an enterprise bus infrastructure for
communication and management of services.
– Provide integration architecture between the
various services and existing and newly developed
applications used in business processes.
– Provide a specialized language for composition
of applications into business processes.

PalGov © 2011 15

Relation between SOA, web services, ESB, and
BPEL

Source, [3]

PalGov © 2011 16

Web service context

• Web services are a distributed architecture:
– The distributed computing paradigm started with DCE
(Distributed Computing Environment) RPC (Remote
Procedure Call), and messaging systems.
– Then the following emerged, distributed objects and
ORBs (Object Request Brokers), such as CORBA
(Common Object Request Broker Architecture), DCOM
(Distributed Component Object Model), and RMI
(Remote Method Invocation).
– Based on them component models, such as EJB
(Enterprise Java Beans), COM+ (Component Object
Model), .NET Enterprise Services, and CCM (CORBA
Component Model) have been developed.

PalGov © 2011 17

BP example

Source, [3]

PalGov © 2011 18

Session Outlines

 Introduction
 Partners

PalGov © 2011 19

BPEL: Important features

• Describe the logic of business processes through
composition of services
• Compose larger business processes out of smaller
processes and services
• Handle synchronous and asynchronous (often
long-running) operation invocations on services,
and manage callbacks that occur at later times
• Invoke service operations in sequence or parallel

PalGov © 2011 20

BPEL: Important features, cont.

• Selectively compensate completed activities in
case of failures
• Maintain multiple long-running transactional
activities, which are also interruptible
• Resume interrupted or failed activities to
minimize work to be redone
• Route incoming messages to the appropriate
processes and activities

PalGov © 2011 21

BPEL: Important features, cont.

• Schedule activities based on the execution time
and define their order of execution
• Execute activities in parallel and define how
parallel flows merge based on synchronization
conditions

PalGov © 2011 22

Session Outlines

 Introduction
 Partners

PalGov © 2011 23

BPEL for Service Composition

• Business process automation requires standards
• Also, requires a specialized language for
composing services into business processes
• Composition of business processes should
support many process instances, long-running
processes, etc.
• The main goal of BPEL is to standardize the
process of automation between web services.

PalGov © 2011 24

Composition of services in private processes,
Orchestration

• A central process (which can be another web
service):
– Takes control over the involved web services
– Coordinates the execution of different operations on
the web services involved in the operation.

PalGov © 2011 25

Orchestration

Source, [3]

PalGov © 2011 26

Composition of services in public processes,
Choreography

• Each web service involved in the choreography
knows exactly when to execute its operations and
whom to interact with.
• Choreography is a collaborative effort focused on
exchange of messages in public business
processes

PalGov © 2011 27

Choreography

Source, [3]

PalGov © 2011 28

Session Outlines

 Introduction
 Partners

PalGov © 2011 29

Developing BP with BPEL

• BPEL uses an XML-based vocabulary that
allows us to specify and describe business
processes.
• With BPEL, we can describe business
processes in two distinct ways:
– Executable business processes specify the exact
details of business processes and can be executed
by a BPEL engine.
– Abstract business processes specify only the public
message exchange between parties, without
specific details of process flows.

PalGov © 2011 30

Partner Links

• When we describe a business process in BPEL, we
actually define a new web service that is a
composition of existing services.
• Developing BPEL processes requires a good
understanding of WSDL and other related
technologies.
• BPEL introduces WSDL extensions, which enable
us to accurately specify relations (partner links)
between several web services in the business
process.

PalGov © 2011 31

BPEL process and its partner links

Source, [3]

PalGov © 2011 32

BPEL Core Concepts

• A BPEL process consists of steps “activities”,
• Two types: basic and structured activities.
• Seven basic activities:
1. Invoking other web services, using <invoke>
2. Waiting for the client to invoke the business process
through sending a message, using <receive>
(receiving a request)

PalGov © 2011 33

Basic activities, cont.

• Cont.:
3. Generating a response for synchronous
operations, using <reply>
4. Manipulating data variables, using <assign>
5. Indicating faults and exceptions, using
<throw>
6. Waiting for some time, using <wait>
7. Terminating the entire process, using
<terminate>

PalGov © 2011 34

BPEL structured activities
1. Sequence (<sequence>) for defining a set of
activities that will be invoked in an ordered
sequence
2. Flow (<flow>) for defining a set of activities that
will be invoked in parallel
3. Case-switch construct (<switch>) for
implementing branches
4. While (<while>) for defining loops
5. The ability to select one of a number of alternative
paths, using <pick>

PalGov © 2011 35

Simple BPEL process example

• Select the best insurance offer from several
• We first declare the partner links to the BPEL
process client (called client) and two
insurance web services (called insuranceA
and insuranceB):

PalGov © 2011 37

Example, Cont.

<?xml version="1.0" encoding="utf-8"?>
<process name="InsuranceSelectionProcess"
targetNamespace="http://companyx.com/bpe
l/example/"
xmlns="http://schemas.xmlsoap.org/ws/200
3/03/business-process/"
xmlns:bpws="http://schemas.xmlsoap.org/w
s/2003/03/business-process/"
xmlns:ins="http://companyx.com/bpel/insu
rance/"
xmlns:com="http://companyx.com/bpel/comp
any/" >

PalGov © 2011 38

Example, Cont.

• The two insurance web services (called insuranceA and
insuranceB):
<partnerLinks>
<partnerLink name="client"
partnerLinkType="com:selectionLT"
myRole="insuranceSelectionService"/>
<partnerLink name="insuranceA"
partnerLinkType="ins:insuranceLT“
myRole="insuranceRequester"
partnerRole="insuranceService"/>
<partnerLink name="insuranceB"
partnerLinkType="ins:insuranceLT"
myRole="insuranceRequester"
partnerRole="insuranceService"/>
</partnerLinks>

PalGov © 2011 39

Example, Cont.

• Declare variables for:
– The insurance request (InsuranceRequest),
– Insurance A and B responses
(InsuranceAResponse,
InsuranceBResponse),
– The final selection
(InsuranceSelectionResponse)

PalGov © 2011 40

Example, Cont.

...
<variables>

<variable name="InsuranceRequest"
messageType="ins:InsuranceRequestMessage"/>

<variable name="InsuranceAResponse"
messageType="ins:InsuranceResponseMessage"/>

<variable name="InsuranceBResponse"

<variable name="InsuranceSelectionResponse"
</variables>
...

PalGov © 2011 41

Example, Cont.

• Finally, we specify the process steps:
– First we wait for the initial request message from the
client (<receive>)
– Then we invoke both insurance web services
(<invoke>) in parallel using the <flow> activity.
– The insurance web services return the insurance
premium.
– Then we select the lower amount
(<switch>/<case>) and return the result to the
client (the caller of the BPEL process) using the
<reply> activity.

PalGov © 2011 42

Example, Cont.

...
<sequence>

<receive partnerLink="client"
portType="com:InsuranceSelectionPT"
operation="SelectInsurance"
variable="InsuranceRequest"
createInstance="yes" />

PalGov © 2011 43

Example, Cont.


<flow>

<invoke partnerLink="insuranceA"
portType="ins:ComputeInsurancePremiumPT"
operation="ComputeInsurancePremium"
inputVariable="InsuranceRequest"
outputVariable="InsuranceAResponse" />

<invoke partnerLink="insuranceB"
portType="ins:ComputeInsurancePremiumPT"
operation="ComputeInsurancePremium"
inputVariable="InsuranceRequest"
outputVariable="InsuranceBResponse" />
</flow>

PalGov © 2011 44

Example, Cont.


<switch>
<case condition = "bpws:getVariableData
('InsuranceAResponse',
'confirmationData',
„/confirmationData/ins:Amount')
<= bpws: getVariableData
('InsuranceBResponse',
'confirmationData',
„/confirmationData/ins:Amount')">

<assign>
<copy>
<from variable="InsuranceAResponse" />
<to variable="InsuranceSelectionResponse" />
</copy>
</assign>
</case> PalGov © 2011 45

Example, Cont.

<otherwise>

<assign>
<copy>
<from variable="InsuranceBResponse" />
<to variable="InsuranceSelectionResponse" />
</copy>
</assign>
</otherwise>
</switch>

<reply partnerLink="client"
portType="com:InsuranceSelectionPT"
operation="SelectInsurance"
variable="InsuranceSelectionResponse"/>
</sequence>
</process> PalGov © 2011 46

Summary

During this module we have explained with
examples how to use business process execution
language BPEL; the following subject have been
covered:
1. Partners
2. BPEL: Important features
3. BPEL for Service Composition
4. Developing BP with BPEL
5. BPEL process example
Next module will cover the UDDI

PalGov © 2011 47

References

1. Sanjiva Weerawarana, Francisco Curbera, “Business Process with
BPEL4WS: Understanding BPEL4WS”, IBM TJ Watson Research Center,
2002
2. Frank Leymann, Dieter Roller, “Business processes in a web services world”,
IBM Software Group, 2002
3. Matjaz B. Juric, Benny Mathew and Poornachandra Sarang, Business
Process Execution Language for Web Services , Second Edition, Packt
Publishing , 2006.

PalGov © 2011 48

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