Ashley,

Strictly speaking, HATEOAS is a constituent part of the Uniform
Interface constraint:

"5.1.5 Uniform Interface
...
In order to obtain a uniform interface, multiple architectural
constraints are needed to guide the behavior of components. REST is
defined by four interface constraints: identification of resources;
manipulation of resources through representations; self-descriptive
messages; and, hypermedia as the engine of application state. These
constraints will be discussed in Section 5.2." [1]

Regards,
Alan Dean

[1] http://roy.gbiv.com/pubs/dissertation/rest_arch_style.htm#sec_5_1_5

On Thu, Dec 4, 2008 at 10:28 AM, Ashley at Metamaxim
<[EMAIL PROTECTED]> wrote:
> Hi Alan
>
> Shouldn't "Hypermedia as the engine of application state" be in the list?
>
> Rgds
> Ashley
>
> Alan Dean wrote:
>
> Can we be a little scientific about this discussion?
>
> Roy stipulates [1] the derivation of REST as:
>
> Style = nil
> Style += Client/Server
> Style += Stateless
> Style += Caching (optional)
> Style += Uniform Interface
> Style += Layered System
> Style += Code on Demand (optional)
>
> So long as the architecture of your system falls within these
> constraints, your system can be considered RESTful. If your system
> breaches a constraint, it is isn't RESTful. There is no such thing as
> 'partially' RESTful [2] which doesn't mean that you can't relax the
> constraints [3] just don't call the resulting system RESTful.
>
> In my experience, the most frequently breached constraint in
> non-trivial systems is statelessness. The next most-often breached
> constraint is the uniform interface. This is entirely anecdotal.
>
> I don't have any numbers, but what is needed to clarify this
> discussion is an estimate of the number of systems without breached
> constraints.
>
> I have no idea which side of the current discussion this assists (if any).
>
> Regards,
> Alan Dean
>
> [1] http://tinyurl.com/56nrp8 (slide 40 onwards)
> [2] http://tinyurl.com/5e4ghv
> [3] http://tinyurl.com/6kojzx
> [see also] http://tinyurl.com/6qgcat
> [see also] http://delicious.com/alan.dean/rest+roy.fielding
>
>
> 

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