The document discusses the integration of RESTful web services with Business Process Management (BPM), highlighting the potential for simple and flexible workflow-driven applications. It presents challenges and solutions related to driving process execution, monitoring tasks, and utilizing hypermedia principles. The conclusion emphasizes that REST resources provide an effective abstraction for publishing processes online and can enhance BPM as a modeling tool for service design.

1. Business Process Management
with REST
Cesare Pautasso
Faculty of Informatics
University of Lugano, Switzerland
c.pautasso@ieee.org
http://www.pautasso.info
@pautasso

2. BPM REST
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3. Business
RESTful
Process
Web Services
Management
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4. WS-* Standards Stack
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5. WS-* Standards Stack
BPM Management
Interoperability
Transactions
Security
Reliability
Metadata
State
Messaging
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6. BPM Management
Interoperability
Transactions
Security
Reliability
Metadata
State
Messaging
Can you do it
with REST?
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7. From REST-* (JBoss)
“ We believe there is huge potential to
http://www.jboss.org/reststar/specifications/workflow.html
marrying REST with workflow and BPM.
[…]
Combined with the architecture of the Web,
a workflow service can provide both a truly
simple, portable, and flexible way to build
workflow driven integrations and
”
applications.
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8. Business Process Management
BPMN/WS-BPEL
Workflow Workflow
Process Model Users/Clients Participants
Act 2 Act 4
Act 1 Act 5 Act 7
Act 3 Act 6
Workflow Management Engine
Workflow
Modelers
Adapters Bus
Applications Web
Services
Databases
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9. WS-BPEL Primitives
Web <receive>
<invoke>
Service <reply>
<invoke> Web
<receive>
Service
 The modeling language natively supports
the RPC or message-based connectors
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10. What is your SOA connector today?
RPC ESB
REST/HTTP
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11. REST as a new connector
RPC ESB
Publish/Subscribe
Call
REST/HTTP
Get/Put/Post/Delete
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12. Is REST really used?
Atom, 2%
Gdata, 1%
XMPP, 0%
JavaScript, 6%
XML-RPC, 2%
SOAP, 17% JSON-RPC, 0%
SMS, 2042 APIs
0%
RSS, 1%
ProgrammableWeb.com
30.6.2010
REST,
71%
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13. REST in one slide
 Web Services expose their
data and functionality trough PUT
resources identified by URI
R
 Uniform Interface Principle: GET
Clients interact with resources POST
through a fix set of verbs. DELETE
Example HTTP:
GET (read), PUT (update), DELETE, POST (catch all),
 Multiple representations for the same resource
 Hyperlinks model resource relationships and valid
state transitions for dynamic protocol description
and discovery
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14. Business Process Management
Workflow Workflow
Process Model Users/Clients Participants
Act 2 Act 4
Act 1 Act 5 Act 7
Act 3 Act 6
RESTful Workflow Management Engine
PUT
GET
R Adapters Bus
Applications Web
Services
POST
DELETE Databases
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15. BPM with REST
Process Model
Publishing
Act 2 Act 4 R Processes
Act 1 Act 5 Act 7
as Resources
Act 3 Act 6
RESTful Workflow Management Engine
RESTful
Service
R R R Composition
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16. BPM with REST
Publishing
This talk will R Processes
focus here as Resources
RESTful Workflow Management Engine
RESTful
Service
R R R Composition
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17. Some Challenges for BPM engines
 Can you drive the execution of tasks with
PUT/POST/DELETE requests?
 Can you monitor your processes with an
RSS/ATOM feed?
 Can you bookmark a process instance?
 Can you send an email to your colleague with a
link to a task from your worklist?
 Can you ask a process to give you links to its
tasks left to be done?
 Can you publish your process as a resource?
 Can you publish resources from your process?
 Can you call RESTful APIs directly?
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18. BPM REST
 Processes  Resources/URIs
 Tasks  Uniform
 Control Flow Interface
 Data Flow  Representations
…  Hypermedia
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19. Everything is a resource
/process/X /process/X/1
Process
Process
Instance
Task
Task
Instance
/task/Y
/task/Y/1
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20. Hypermedia
/process Process
Process
Instance
GET
/process/name Task
Task
Instance
GET
/process/name/instance
GET
/process/name/instance/taskname
Follow links to discover the processes
deployed as resources
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21. Representations
Web page
with form to start List of process
a new process input parameters
instance ContentType: ContentType:
text/html application/xml
GET /process/name
ContentType: ContentType:
text/plain application/json
ContentType:
Basic textual Process
description image/svg+xml metadata
of the process in JSON
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22. Uniform Interface and Hypermedia
List the
GET /process deployed Get a form
processes describing how
GET /process/name to start the
process
Start a new
POST /process/name process
instance Check what
is the state
GET /process/name/instance of the
instance
DELETE /process/name/instance
Clean up
(once it is done)
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23. Starting or Running a new process?
/process  Should the client be kept
waiting for the process to run
until completion?
POST /process
200 OK  Clients may want to block until
(Process the whole process has
Finished completed its execution
Reply) (or it decides to reply to them)
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24. Starting or Running a new process?
/process  The client starting a long
running process is redirected to
a location x representing the
POST /process newly started process instance
 The process and the client run
202 Accepted asynchronously
Location: x
 The client may retrieve the
current state of the process
GET /process/x instance at any time
200 OK
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25. Uniform Interface and Hypermedia
GET /task List the
active tasks Get a form
describing how
GET /task/name/instance to perform the
task
Finish
POST /task/name/instance
the task
GET /task/name/instance Get the final
representation
of the completed
… task
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26. POST or PUT?
GET /task Note:
PUT could also be
used here
GET /task/name/instance to set the state
(Finished, Failed)
of the task
POST /task/name/instance
GET /task/name/instance
…
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27. Example: RESTBucks
Jim Webber, Savas Parastatidis, Ian Robinson http://restinpractice.com/ 27

28. Simple RESTBucks Example
POST
/rest/restbucks/order/1.0/
/rest/restbucks/order/1.0/{id}
GET
/tasks/restbucks/order/1.0/{id}/payment
POST
GET
/receipt/{uuid}
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29. Simple RESTBucks Example
Hypermedia-centric service design (and implementation)
done with a business process model
Private Tasks
Resources
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30. Instantiating a process
GET /rest/restbucks/order/1.0/
Retrieve a form which describes how to instantiate a new process
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31. Instantiating a process
POST /rest/restbucks/order/1.0/
Run = blocking
(client waits until
Start = non blocking the process replies)
(redirect to URI of
the new instance)
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32. Interacting with a task
GET
/task/restbucks/order/1.0/0/payment
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33. Interacting with a task
POST /rest/restbucks/order/1.0/0/payment
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34. Interacting with a resource
GET /receipt/2fc7f6e2-8b43-4672-a7c4…
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35. Interacting with a resource
DELETE /rest/restbucks/order/1.0/0
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36. Deleting a process resource
DELETE /rest/restbucks/order/1.0/0
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37. Viewpoints
Control Data
Flow Flow
Service
Bindings
REST.TASK REST.URI REST WS-* SQL …
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38. Control
Flow
Control Flow
Dependency
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39. Service
Bindings
SQL
WS-*
REST
REST.URI
REST.TASK
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40. REST.TASK
Specify the final state
of the Payment task
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41. REST.URI
Specify the state
associated with the URI
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42. Data
Flow
Data Flow
(Copy)
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43. ©2010 - Cesare Pautasso 43

44. Static vs. Dynamic Typing
 Myth: RESTful Web services cannot be
composed (with BPEL) because they do
not give a static contract description
 Reality: RESTful Web services can
dynamically negotiate the most
suitable representation format with
their clients
 Challenge: How to support dynamic
typing and content type negotiation in a
BPM composition language?
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45. Active Resources
 Myth: Processes cannot be mapped to
resources because they can change
their state (independently of their
clients)
 Reality: REST Resources do not have to
be passive “CRUD” services but can be
active and have a life of their own.
 Challenge: How to best let clients
control an active resource backed up
by a process instance through the
uniform interface?
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46. Synchronous vs. Asychronous
 Myth: Processes run for a long time
and need to interact asynchronously
with their clients. This cannot be done
with HTTP.
 Reality: HTTP supports non blocking
interactions. Each process instance is
mapped to a resource URI, which can
be used by clients throughout its
lifetime.
 Challenge: How to let processes send
notifications back to their clients?
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47. Conclusions
 REST resources are a good abstraction
to publish processes on the Web
 RESTful HTTP is good enough to
interact without any extension with
process execution engines and drive
the execution of process and task
instances
 If done right, BPM can be a great
modeling tool for Hypermedia-centric
service design
(and implementation!)
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48. More Information
Cesare Pautasso
Faculty of Informatics, USI Lugano
http://www.pautasso.info/
@pautasso
JOpera
RESTful Process Engine
http://www.jopera.org/
@jopera_org
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49. References
 R. Fielding, Architectural Styles and the Design of Network-
based Software Architectures, PhD Thesis,
University of California, Irvine, 2000
 C. Pautasso, O. Zimmermann, F. Leymann, RESTful Web
Services vs. Big Web Services: Making the Right Architectural
Decision, Proc. of the 17th International World Wide Web
Conference (WWW2008), Bejing, China, April 2008
 C. Pautasso, BPEL for REST, Proc. of the 7th International
Conference on Business Process Management
(BPM 2008), Milano, Italy, September 2008
 C. Pautasso, Composing RESTful Services with JOpera,
In: Proc. of the International Conference on Software
Composition (SC2009), July 2009, Zurich, Switzerland.
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50. Conclusion
Raj Balasubramanian,
 Applying the SOA composition principle to
Benjamin Carlyle,
Thomas Erl,
REST gives interesting results Pautasso,
Cesare
 Thanks to hyperlinks, REST SOA with a new
brings REST,
(more dynamic and loosely coupled)
Prentice Hall,
twist to SOA composition to appear in 2011
 Composing RESTful services helps to build
mashups, but is different
 A RESTful API is the perfect abstraction for
publishing the state of a workflow
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