This document introduces REST (Representational State Transfer), an architectural style for designing web services. It discusses what REST is, compares RESTful and SOAP-based approaches, and provides resources for learning more. The document also summarizes the key principles of REST including uniform interface, statelessness, and hypermedia as the engine of application state. Finally, it discusses designing RESTful services and provides examples from Delicious.

1. Introducing REST
Dong Liu
Dept. of Computer Science
Univ. of Saskatchewan
dong.liu@usask.ca
http://blogs.usask.ca/dong_notes/

2. Agenda
What is REST
RESTful services
Comparing RESTful and SOAP-based
approaches
Useful resources
Jan. 8 2008 Dong Liu

3. REST
Representational State Transfer
The term comes from Roy Fielding’s PhD work
More practical than theoretical
It is an architectural style, not a technology, nor
an architecture
Software architecture = {Elements, Constraints,
Rationale} *
An architectural style abstracts elements and
constraints from various specific architectures *
Analogy: designs and design pattern
* Perry & Wolf quot;Foundations for the study of software architecture,quot; SIGSOFT Softw. Eng. Notes. ACM,
vol. 17, pp. 40-52, 1992.
Jan. 8 2008 Dong Liu

4. Deriving REST
RR: replicated repository
from Roy T. Fielding quot;Architectural styles and the design of network-based software
architectures,quot; University of California, Irvine, 2000. $: cache
CS: client-server
LS: layered system
S: stateless
VM: virtual machine
COD: code on demand
U: uniform interface
Jan. 8 2008 Dong Liu

5. Uniform interface
Resources are identified by ONE resource
identifier mechanism
Access methods are the same for all
resources
Resources are manipulated by exchanging
representations
Representations are in self-descriptive
messages
Hypermedia acts as the engine of
application state
Jan. 8 2008 Dong Liu

6. REST rationale
Maximize reuse
Minimize coupling
Eliminate partial failure condition
Scale without bound
Simplify
from Roy T. Fielding quot;The Rest of REST,quot; RailsConf Europe, 2007.
Jan. 8 2008 Dong Liu

7. Generic process to design RESTful services
1. Identify resources
2. Design URIs
3. Expose a subset of the uniform interface
4. Design the representations from and to the
client
5. Integrate this resource into existing
resources, using hypermedia links and forms
6. Consider typical flows
7. Consider error conditions
A revised version of P216 in Leonard Richardson & Sam Ruby quot;RESTful Web Services,quot; O'Reilly, 2007.
Jan. 8 2008 Dong Liu

8. RESTful design of del.icio.us services (1)
The example comes from Leonard Richardson & Sam Ruby quot;RESTful Web Services,quot; O'Reilly, 2007.
Jan. 8 2008 Dong Liu

9. RESTful design of del.icio.us services (2)
Jan. 8 2008 Dong Liu

10. RESTful design of del.icio.us services (3)
Jan. 8 2008 Dong Liu

11. WS stack
from http://www.innoq.com/resources/ws-standards-poster/
Jan. 8 2008 Dong Liu

12. Interoperability?
Support for the Basic Profile is the
baseline for interoperable Web services.
from http://www.ws-i.org/Default.aspx
Customers should demand that all of
their Web services-enabled technology
be compliant with the Basic Profile, and
that in turn will lay the foundation for
Web services to fulfill their promise and
provide technology independent
interoperability.
Dan Sholler, Gartner
Jan. 8 2008 Dong Liu

13. WS-Babel
from http://www.flickr.com/photos/psd/1805565187/in/set-72157602805227511/
Jan. 8 2008 Dong Liu

14. WS-Addressing
from http://www.flickr.com/photos/psd/406077535/in/set-72157602131510927/
Jan. 8 2008 Dong Liu

15. Jan. 8 2008
The Web is agreement
Dong Liu from http://www.archive.org/details/TheWebIsAgreement

16. Two must-read’s
Jan. 8 2008 Dong Liu

17. The community
Yahoo rest-discuss group
Steve Vinoski
Paul Downey
Sam Ruby
Bill de hÓra
Joe Gregorio
Mark Nottingham
Pete Lacey
Stefan Tilkov
Stuart Charlton
Mark Baker
…
Jan. 8 2008 Dong Liu

18. Thanks