Web Service Choreography Configurations for BPMN

Third International Workshop on Engineering Service-Oriented Applications:
Analysis, Design and Composition
WESOA’07 – http://wesoa07.googlepages.com/

Web Service Choreography
Configurations for BPMN

Kerstin Pfitzner1, Gero Decker2, Oliver Kopp1, Frank Leymann1

Motivation
configurations
BPMN needed
transformation
instead of manual steps
BPEL4Chor
transformation

set of abstract
BPEL processes
executable completion
(manual work)
set of executable
BPEL processes
Presented by Oliver Kopp 2
© Kerstin Pfitzner, Gero Decker, Oliver Kopp, Frank Leymann

Agenda

Orchestrations and Choreographies

BPEL4Chor
Extensions for BPEL to model
choreographies

Configurations for BPMN to support
modeling BPEL4Chor


Bookshop orchestration
Supplier
Client Book shop

Not
request
found
price

update
suppliers
data

no price
price received
received

select
send not cheapest
found supplier

send
response

De facto standards:
BPMN, BPEL

The bookshop choreography - pure BPMN
Supplier
Client Book shop

calculate
send price
price
request

Not book
request book found
found not found
price

update
suppliers
reply
data
not found

reply

no price
price received
received

select
send not cheapest
found supplier

send
De facto standard:
response

BPMN

Other languages to model choreographies
Interaction model
Interconnection model
(simplified)
Supplier
Client Book shop

Client Book shop
(c) (bs)
calculate
send price
price
request

Order
Not book
request book found
found not found
price

update
suppliers
reply
data
for each element in S (concurrent) (bs)
not found

Book shop Supplier
reply

(bs) (S)

Price Request
no price
price received
received

Supplier Book shop
select
send not cheapest
found
(S) (bs)
supplier

Response
send
response

Book shop Client
Let’s Dance,
(bs) (c)

Offer
WS-CDL
BPEL4Chor

BPEL4Chor

Includes all features of BPEL 2.0, e.g.
Event handler
Termination handler
Uses abstract BPEL
Plus choreography information
Notion of participants
Multiplicity of participants
Participant references


BPEL4Chor Participant Behavior Descriptions
Client
<sequence> Book shop

<invoke
wsu:id=“sendPriceRequest” send price
request

/> Not
request
found
price

<pick> update
suppliers
data

<onMessage
wsu:id=“receivePrice” />
<onMessage
no price

wsu:id=“receiveNotFound” price received
received

select

/> send not cheapest
found supplier

</pick> send
response

</sequence>


BPEL4Chor Participant Topologies
<topology name=“bookshopquot; …>

<participantTypes> Supplier
Client Book shop

<participantType
name=“BookShopquot;
participantBehaviorDescription
=“mychor:BookShopquot; />
<participantType
name=“Supplier“ … /> …
</participantTypes>

<participants>
<participant name=“bquot;
type=“BookShopquot; />
<participantSet name=“suppliers”
type=“Supplier”
<participant
name=“currentSupplier” />
</participantSet>
…

BPEL4Chor Participant Topologies
Client Book shop

<messageLinks> send price
request

<messageLink Not
request
found
price

sender=“c“ update
suppliers

sendActivity=“sendPriceRequest” data

receiver=“BookShop“
receiveActivity=“getOrder”
messageName=“orderquot; /> … no price
price received
</messageLinks>
received

select
send not cheapest
found supplier

send
response


Configurations for BPMN

12

What is missing in BPMN?

Features of BPEL 2.0
Event handler
Termination handler
BPMN: only termination of transactional sub-processes
Certain choreography information
Multiplicity of participants
Participant references


BPEL basic activities
Basic activities distinguished by marking


BPEL4Chor data types

Rendering of the different variable types of BPEL


Reference passing

There exist only one instance of Z
This instance is created by X
The reference to Z needs to be passed to Y


Pool sets and references

Pool sets contain multiple instances of one participant
Sender and receiver have to be specified, if there are
multiple instances of them


Iteration over a participant set

Specification of
Set to iterate on
Name of the current
participant reference


BPEL handlers

invoke
synch.

...
... ...
...

Different handlers distinguished by marking
Event Handler
Fault Handler
Termination Handler
Compensation Handler


Bookshop choreography / configured BPMN
Supplier
Client Bookshop

suppliers

calculate
send price
price
request current
supplier
book
not
request not found book found
found
price

update
suppliers reply
data not found

reply

no price
price received
received

select
send not
cheapest
found
supplier

send not
found


Transform configured BPMN to BPEL4Chor

Extending existing transformation
Ouyang et al.: Pattern-based translation of BPMN
process models to BPEL web services
Adopting restrictions:
Exclusion of e.g.
Ad-hoc or transactional sub-processes
End-events with triggers
Tasks of type user, script, abstract, manual reference, non-
typed
Excluded support of arbitrary cycles
BPMN configuration respected in the mapping


Summary

BPEL4Chor as choreography extension of BPEL
Multiple participants of one type
Configurations of BPMN to fully support modeling
of BPEL4Chor
Ongoing work
Implementation of mapping of configured BPMN to
BPEL4Chor
Interaction models vs. interconnection models
Future work
Evaluation


Web Service Choreography Configurations for BPMN

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Web Service Choreography Configurations for BPMN