Push-Enabling RESTful Business Processes Cesare Pautasso
Faculty of Informatics, University of Lugano, Switzerland
[email protected] http://www.pautasso.info @pautasso 6.12.2011
Erik Wilde EMC
[email protected] http://dret.net @dret
RESTful Business Processes Cesare Pautasso
Faculty of Informatics, University of Lugano, Switzerland
[email protected] http://www.pautasso.info @pautasso 6.12.2011
Erik Wilde EMC
[email protected] http://dret.net @dret
Abstract Representational State Transfer (REST) as an architectural style for service design has seen substantial uptake in the past years. However, some areas such as Business Process Modeling (BPM) and push services so far have not been addressed in the context of REST principles. In this work, we look at how both BPM and push can be combined so that business processes can be modeled and observed in a RESTful way. Based on this approach, clients can subscribe to be notied when certain states in a business process are reached. Our goal is to design an architecture that brings REST's claims of loose coupling and good scalability to the area of BPM, and still allow process-driven composition and interaction between resources to be modeled.
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BPM ©2011 - Cesare Pautasso
REST 4
Business Process Management
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RESTful Web Services
5
RESTful APIs…
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RESTful APIs…
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WS-* Standards Stack
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WS-* Standards Stack Management
State
Transactions
Security
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Reliability
Metadata
Interoperability
BPM
Messaging 9
Management
State
Transactions
Security
Reliability
Metadata
Interoperability
BPM
Messaging Can you do
with REST? ©2011 - Cesare Pautasso
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“
We believe there is huge potential to 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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http://www.jboss.org/reststar/specifications/workflow.html
From REST-*
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REST in one slide Web Services expose their PUT data and functionality trough resources identified by URI R GET Uniform Interface constraint: Clients interact with resources POST DELETE through a fix set of verbs. Example HTTP: GET (read), POST (create), PUT (update), DELETE Multiple representations for the same resource Hyperlinks model resource relationships and valid state transitions for dynamic protocol description and discovery ©2011 - Cesare Pautasso
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“
We believe there is huge potential to marrying REST with workflow and BPM. The HATEOAS (hypermedia and linking) principal of REST is logically a dynamic state machine and fits very well with how workflow and BPM systems are designed. 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. ©2011 - Cesare Pautasso
http://www.jboss.org/reststar/specifications/workflow.html
From REST-*
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Business Process Management Workflow Users/Clients
Process Model Act 4
Act 2 Act 1
Act 5 Act 3
Workflow Participants
Act 7
Act 6 RESTful Workflow Management Engine
PUT GET
R
POST
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Adapters Applications
DELETE
Bus Web Services
Databases 14
BPM with REST Process Model Act 2 Act 1
Act 5 Act 3
R
Act 4 Act 7
Publishing Processes as Resources
Act 6 RESTful Workflow Management Engine
R ©2011 - Cesare Pautasso
R
R
RESTful Service Composition 15
BPM with REST
BPEL for REST BPMN for REST
R
Publishing Processes as Resources
RESTful Workflow Management Engine
R ©2011 - Cesare Pautasso
R
R
RESTful Service Composition 16
BPM with REST
R
We are here
Publishing Processes as Resources
RESTful Workflow Management Engine
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R
R
RESTful Service Composition 17
BPM Processes Tasks Control Flow Data Flow … ©2011 - Cesare Pautasso
REST Resources/URIs Uniform Interface Representations Hypermedia 18
Everything is a resource /process/X
Process
Process Instance
Task
Task Instance
/task/Y
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/process/X/1
/task/Y/1 19
Hypermedia /process
Process
Process Instance
Task
Task Instance
GET /process/name GET /process/name/instance GET /process/name/instance/taskname
Follow links to discover the processes deployed as resources ©2011 - Cesare Pautasso
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Representations Web page with form to start a new process ContentType: instance
ContentType:
BPMN2.0 process source code
text/html application/bpmn+xml GET /process/name
ContentType:
text/plain Basic textual description of the process ©2011 - Cesare Pautasso
ContentType:
ContentType:
application/json
image/svg+xml
Process metadata in JSON 21
Uniform Interface and Hypermedia GET /process GET /process/name POST /process/name
List the deployed processes
Get a form describing how to start the process Start a new process instance Check what
GET /process/name/instance DELETE /process/name/instance ©2011 - Cesare Pautasso
is the state of the instance
Clean up (once it is done) 22
Starting or Running processes? /process Should the client be kept
POST /process
200 OK (Process Finished Reply) ©2011 - Cesare Pautasso
waiting for the process to run until completion?
Clients may want to block until the whole process has completed its execution (or it decides to reply to them) 23
Starting or Running processes? /process The client starting a long
POST /process 202 Accepted Location: x GET /process/x
running process is redirected to a location x representing the newly started process instance The process and the client run asynchronously The client may retrieve the current state of the process instance at any time
200 OK
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Push vs. Pull Notification /process Problem: how can the process
instance tell the client that it has reached a certain state?
GET /process/x 200 OK
PULL
Easy to use a PULL-based event notification with HTTP
PUSH
Can we also support PUSHbased event notification with HTTP?
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Push-Enabling RESTful Business Processes Cesare Pautasso
Faculty of Informatics, University of Lugano, Switzerland
[email protected] http://www.pautasso.info @pautasso 6.12.2011
Erik Wilde EMC
[email protected] http://dret.net @dret
What is your SOA connector?
RPC
BUS
REST/HTTP
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REST as a new connector
RPC
BUS Publish/Subscribe
Call
REST/HTTP Get/Put/Post/Delete ©2011 - Cesare Pautasso
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What about event notifications?
BUS
RPC
Publish/Subscribe Callback
REST/HTTP
?
Get/Put/Post/Delete ©2011 - Cesare Pautasso
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Solutions
1.Web Feeds (PubSubHubbub) 2.HTTP Long Polling 3.Inverted REST (HTTP Callbacks) 4.WebSockets 5.(XMPP)
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Representations GET /process/name ContentType:
application/atom+xml Web feed representing the collection of process instances with links to each instance 31
Representations GET /process/name/instance ContentType:
application/atom+xml Web feed representing the current state of the process instance (collection of task instances) 32
Loan Approval Example Process Published as a Resource
External Resources
Task Published as a Resource ©2011 - Cesare Pautasso
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Process as a Web Feed Loan Approval Process Instance x http://rest.jopera.org/loan/x 2011-06-10T11:11:30Z Cesare
[email protected] Choose Task (Ready) http://rest.jopera.org/loan/x/choose 2011-06-10T11:12:20Z State: ready Approve Task (Waiting) http://rest.jopera.org/loan/x/approve 2011-06-10T11:11:30Z State: waiting ©2011 - Cesare Pautasso
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BPM Process Instance Task Process User Task State Task Timestamp Task Instance URI ©2011 - Cesare Pautasso
Feed Feed Feed Entry Feed Author Summary Updated Link 35
Link Relations Loan Approval Process Instance x http://rest.jopera.org/loan/x
Template Process
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Process Instance
Self
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PubSubHubbub Get Feed Consumer
Feed
Hub Subscribe
Feed Producer
Ping
Hub
Notify/Poll ©2011 - Cesare Pautasso
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Architecture
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Conclusion Thanks to hypermedia, URIs and the HTTP uniform interface, REST resources are a very good abstraction to publish executable business processes on the Web RESTful HTTP is good enough to interact without any extension with process execution engines to drive the execution of process and task instances and to deliver notifications The state of a process instance can be projected to be represented as a standard Web feed The PubSubHubbub protocol can be used as an optimization to scale the corresponding delivery of notication callbacks ©2011 - Cesare Pautasso
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References Roy Fielding, Architectural Styles and the Design of Network-based Software Architectures, PhD Thesis, University of California, Irvine, 2000 Leonard Richardson, Sam Ruby, RESTful Web Services, O’Reilly, May 2007 Jim Webber, Savas Parastatidis, Ian Robinson, REST in Practice: Hypermedia and Systems Architecture, O‘Reilly, 2010 Subbu Allamaraju, RESTful Web Services Cookbook: Solutions for Improving Scalability and Simplicity, O’Reilly, 2010 Stevan Tilkov, HTTP und REST, dpunkt Verlag, 2009, http://rest-http.info/ Thomas Erl, Raj Balasubramanians, Cesare Pautasso, Benjamin Carlyle, SOA with REST, Prentice Hall, end of 2010 Martin Fowler, Richardson Maturity Model: steps toward the glory of REST, http://martinfowler.com/articles/richardsonMaturityModel.html ©2009-2010 - Cesare Pautasso, Erik Wilde
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Self-References Cesare Pautasso, Olaf Zimmermann, Frank 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. Cesare Pautasso and Erik Wilde. Why is the Web Loosely Coupled? A MultiFaceted Metric for Service Design, Proc of the 18th International World Wide Web Conference (WWW2009), Madrid, Spain, April 2009. Cesare Pautasso, BPEL for REST, Proc. of the 6th International Conference on Business Process Management (BPM 2008), Milan, Italy, September 2008. Cesare Pautasso, BPMN for REST, Proc. of the 3rd BPMN Workshop (BPMN 2011), Luzern, Switzerland, November 2011 Cesare Pautasso, RESTful Web Service Composition with JOpera, Proc. Of the International Conference on Software Composition (SC 2009), Zurich, Switzerland, July 2009. Cesare Pautasso, Gustavo Alonso: From Web Service Composition to Megaprogramming In: Proceedings of the 5th VLDB Workshop on Technologies for E-Services (TES-04), Toronto, Canada, August 2004. ©2009-2010 - Cesare Pautasso, Erik Wilde
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Raj Balasubramanians, Benjamin Carlyle, Thomas Erl, Cesare Pautasso, SOA with REST, Prentice Hall, 2012
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10th International Conference on Business Process Management (BPM 2012) September 3-6 2012, Tallinn, Estonia http://bpm2012.ut.ee ©2011 - Cesare Pautasso
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16-20 April 2012, Lyon, France http://ws-rest.org/2012 ©2011 - Cesare Pautasso
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PhD Positions Available
Cesare Pautasso http://www.pautasso.info/ @pautasso ©2011 Cesare Pautasso
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