Re: Self-descriptive messages

On Fri, Aug 24, 2012 at 10:14 PM, Darrel Miller <[email protected]> wrote:
> Mark,
>
> The interesting thing about the SKU scenario is that the URI may
> actually capture the users intent more accurately than explicitly
> stating the quantity.  If the request body contains a URI that points
> to http://aonlinestore.com/sku/jumbopackofshrimp then that maybe is
> the exactly what that the user is requesting.  The fact that this week
> a jumbo pack of shrimp contains 10 shrimp and last week it contained 8
> shrimp is irrelevant to the user because the identifier is specifying
> what the user wants.
>
> I believe that to discount the my weathersnapshot scenario based on
> the fact that I used a text/uri-list is addressing a different point.
> I admit that I tend to be somewhat more cavalier about allowing the
> server to pile on semantics to a message than I would ever allow a
> client to do and I realize that't not a good idea.  However, I believe
> the point I was trying to make is just as valid if I were to use
> application/vnd.acme.list-of-uris-to-weather-images.
>
> What are negative effects of allowing a server to dereference a link
> contained in the request to acquire all the information necessary to
> process the request?

It's been a while, I'll take a stab... assuming it's truly a URL and
not a URI...

Performance - the server now has to do the de-referencing of a one or more URLs.

Complexity - the order example requires a transaction and
de-referencing adds to the list of things that can go wrong.

Understandability - from a client perspective, it's less
understandable - guarantees that key attributes (e.g. price) of the
target resource hasn't changed and the like.  maybe that could be
covered by some 'purchasing protocol' or somesuch?

Reliability - if the URL needs to be de-referenced and that server is
unresponsive, your whole system is down.

Visibility - moot, because of POST.

Some are admittedly a stretch:)  What are the advantages?

Thanks,
--tim