Re: CherryPy and REST: REST vs RPC and CherryPy dispatch methods

On Sat, Aug 4, 2012 at 12:56 AM, Nick Gall <[email protected]> wrote:

> **
>
>
> On Fri, Aug 3, 2012 at 6:08 PM, Mike Kelly <[email protected]> wrote:
>
>>
>>
>> On 3 Aug 2012, at 19:35, Nick Gall <[email protected]> wrote:
>>
>>
>>
>> I've never heard that one style of dispatching is more "RESTful" than
>> another. What most differentiates REST from RPC is the what as known as the
>> hypermedia constraint.
>>
>> Hmm, as far as I can tell, REST's main source of differentiation from RPC
>> is the combination of self descriptive messaging and layered constraint
>> which produces a system in which applications are designed as
>> network-visible interactions as opposed to the non-visible invocations you
>> get from RPC. All of the uniform interface subconstraints separate REST
>> from RPC but I think self descriptive messaging is the key one from that pov
>>
>
> Mike, you may have lost me. How does the requirement of self-descriptive
> messaging relate to style of dispatching?
>
> Or are you saying that self-descriptive messaging separates REST from RPC
> more than the hypermedia constraint?
>
> If you are saying the latter, then I would claim that there are lots of
> self-descriptive RPC architectures out there, so self-descriptive messaging
> does NOT separate REST from RPC nearly as much as the hypermedia constraint
> does. I'd also argue that the hypermedia constraint is the one that is
> hardest for those with a traditional RPC mindset to grok, whereas almost
> anyone can grok self-descriptive messaging. So in terms of the mental shift
> required, the hypermedia constraint is also the biggest differentiator.
>
> In fact, in his thesis Roy defines REST in terms of the hypermedia
> constraint: "This chapter introduces and elaborates the Representational
> State Transfer (REST) architectural style for distributed *hypermedia*systems."
> In other words, if you're not doing hypermedia, you're not doing REST.
>
> -- Nick
>

I was saying the latter.. I'm not saying hypermedia is unimportant, just
that it is not the most fundamental aspect in terms of differentiating from
RPC. As far as I can tell this is reflected in the evaluation section of
Roy's thesis:

http://www.ics.uci.edu/~fielding/pubs/dissertation/evaluation.htm#sec_6_5_2

"What makes HTTP significantly different from RPC is that the requests are
directed to resources using a generic interface with standard semantics
that can be interpreted by intermediaries almost as well as by the machines
that originate services. The result is an application that allows for
layers of transformation and indirection that are independent of the
information origin, which is very useful for an Internet-scale,
multi-organization, anarchically scalable information system. RPC
mechanisms, in contrast, are defined in terms of language APIs, not
network-based applications."

Also, even though it wasn't the point I was making, self-descriptive
messaging can and does effect the style of dispatching. On the web, it's
responsible for enabling the existence of web server component frameworks
such as Ruby's "Rack"[1] or node.js's "Connect"[2].

[1] http://rack.rubyforge.org/doc/
[2] http://www.senchalabs.org/connect/

Cheers,
M