Re: [service-orientated-architecture] Re: SOA Reference Architecture

[Anne Thomas Manes]

Spot on, Mark. Harm's example not only missed the mark on REST, it also missed the mark on SOA.

In REST, the center of the design is the resource (the lightbulb). As you've described below, each lightbulb has a unique URL, you retrieve its state via GET, and you set its state via PUT. You might use POST to add additional state, such as its location and its wattage.

In SOA, the center of the design should be the capability (managing lightbulbs). A service exposes that capability through a set of operations:
- locateLightbulbs
  - input (query parameters)
  - output (array of lightbulb identifiers that match the query parameters)
- queryLightbulbs
  - input (array of lightbulb idenitifers)
  - output (array of lightbulb states)
- setLightbulbs
  - input (array of lightbulb identifiers and state settings)
  - output (void or confirmation/fault)

One major distinction, here, is that you can manage multiple lightbulbs through this one service. The service has a unique URL. You identify the lightbulb(s) that you want to query or set as part of the content of the message.

If you want to make it a RESTful service (e.g., apply the REST implementation pattern to this service), then the lightbulb identifier should be a URL, and once you have located a service, you should be able to GET and SET the lightbulb state using GET and PUT in addition to using the service API.

Anne

On 6/30/06, Mark Baker <[EMAIL PROTECTED]> wrote:

Lightbulbs! My favourite REST example. See for yourself;

http://www.markbaker.ca/2002/08/Rest/

> Using the REST approach, following your scheme one would define the resources:
> http://example.lightbulb.net/TurnOn
> http://example.lightbulb.net/TurnOff
> http://example.lightbulb.net/Dim
>
> and the light would be turned on, turned off and dimmed by HTTP/POSTing a message to each of the respective resources.
>
> An alternative scheme would be to have just one resource:
> http://example.lightbulb.net
> and include the name of the operation in the POSTed messages.
>
> Or one could HTTP/GET "queries" like http://example.lightbulb.net/TurnOn and http://example.lightbulb.net/Dim?Luminosity=.75.

None of those are RESTful.

AFAIK, REST suggests just one solution for that problem. A single
identifier for the lightbulb;

http://example.net/lightbulb1234

and the use of PUT to turn the bulb on and off, ala;

PUT http://example.org/lightbulb1234
Content-Type: application/lightbulb+xml
<lightbulb state="on"/>

Simple, no?

Mark.

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