Helping Things to REST

Helping Things to « REST » Web of Things Presentation, part II Dominique Guinard [email_address] Institute for Pervasive Computing, ETH Zurich Lenzerheide, January 2009

Service Oriented Architectures: The WS-* World [ WS Standards, http://www.innoq.com/soa]

Resource Oriented Architectures: The REST World

Resources.

Their names (URIs).

Their representations (JSON, XHTML)

Links between them.

A uniform interface (HTTP).

XHTML HTTP URI

Comparing the Two Worlds

SOA WS-* Approach

HTTP as transporter.

The comp-comp interface is a WSDL.

User Interface?

Testing: stub generation from a WSDL and lots of SOAP messages.

SOA loves XML.

An App Server everywhere.

Heavy.

ROA REST Approach

HTTP as service platform!

The comp-comp interface is the URL.

The UI is the URL/browser.

Testing by typing a URL in your browser (doable?)

ROA loves JSON.

A Web Server everywhere .

Less heavy.

RESTifying the Spots

1. Resource Design

Root: http://webofthings.net/

Resources:

Spots: http://webofthings.net/spots

Spot 2: http://webofthings.net/spots/2

Light Sensor: http://webofthings.net/spots/2/sensors/light

Led Actuator: http://webofthings.net/spots/2/actuators/led/

2. Representation Design

XHTML as default, ideal for browsing:

http://webofthings.net/spots

JSON, ideal for parsing:

http://webofthings.net/spots.json

XML, ideal for integration

http://webofthings.net/spots.xml

3. Uniform Interface [ HTTP: http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol]

3. Uniform Interface

HTTP Verbs: What do you wanna do?

GET: retrieve the representation of a resource.

PUT: create or update a resource.

DELETE: remove a resource.

POST: create a subordinate (or custom: RPC!)

HTTP Headers: What are you sending me?

Metadata:

Content type: application/json, text/html, etc.

Status:

200 OK, 201 Create, 400 Bad Request, 401 Unauthorized

HTTP Body: The meat (or let’s say the carrots):

The content in its representation.

Thoughts and Buzz Use your brains! > don’t design-by-buzzword > don’t believe everything you read > always keep in mind that change is inevitable [ Fielding, Roy. “ A little REST and Relaxation” Jazoon 2007] Cache Authenticate Encrypt Link Share Reuse Stateless Lightweight IPv6 Lowpan Mobile Replicate Cloud Scale