Re: REST and DELETE?

Mark,

On Thu, Aug 9, 2012 at 3:14 PM, Mark Baker <[email protected]> wrote:

> **
>
> That's not self-descriptive, it's just "descriptive".
>
> Self-descriptive is where the message's meaning depends only on the
> message itself (as interpreted by referenced standards).
>
>
This is one of the issues that I still fail to grasp.

Consider that I want to order a item from a store that has their own custom
media type for placing the order.

POST /order
Content-Type: application/vnd.aonlinestore.orderform

<order>
   <partno>1234232323</partno>
   <qty>1</qty>
   <price>51.99</price>
</order>

I am assuming that this message is considered sufficiently self-descriptive
based on the semantics defined in the custom media type spec .  Although, I
do have to trust that the store does not redefine what that part number is
used to represent between the time I create the cart and the time I place
the order.

So what happens if the store decides in it's wisdom to use URIs to identify
products, and so the message would be,

POST /order
Content-Type: application/vnd.aonlinestore.orderform

<order>
   <partno>http://aonlinestore.com/products/1234232323</partno>
   <qty>1</qty>
   <price>51.99</price>
</order>

Now the partno is a link to another resource that describes the product.
 Are we still self-descriptive?

What if the store decided that using SKUs (stock keeping units) was a
better option and so now a quantity isn't necessary.

POST /order
Content-Type: application/vnd.aonlinestore.orderform

<order>
   <sku>http://aonlinestore.com/sku/1234232323Q1</sku>
   <price>51.99</price>
</order>

Now my order is even more dependent on an external resource to identify
what I am buying.

At which point, I don't see the difference between this last message and
going a step further and creating a resource out of my desire to purchase
something, and then using that in my message.

POST /order
Content-Type: text/uri-list

http://aonlinestore.com/user/234/requisition/3453/line/1


As a user, I am expressing the intent "please order the thing I told you
that I wanted to order".  If, as you mention on your blog post, the price
has changed since the requisition was made, the user can still be informed.

I don't understand how it is that we lose self-descriptiveness by using a
link to a resource in our message.  Or have I mis-understood the guidance?

Darrel